Xantia V6 broken exhaust (update: and rough low rpm running)

Tell us your ongoing tales and experiences with your French car here. Post pictures of your car here as well.

Moderators: RichardW, myglaren

User avatar
Mandrake
Posts: 8275
Joined: 10 Apr 2005, 17:23
x 355

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

stevieb wrote:
Mandrake wrote:If you do change the plug leads make sure you change the top inlet manifold gasket (a couple of quid from Citroen/Peugeot) and I would take the opportunity to change the spark plugs too. Make sure you fit only the correct types - Bosch FR8KDC. I had a different type in at one point and had problems with plug fouling! Not with these ones. This engine seems to be fussy about the plugs you use.
Ah, the last time I bought an inlet manifold gasket I bought two, seeing as they were so cheap... :wink:
I bought three last time. :twisted: I had taken the inlet manifold off so many times during a years worth of troubleshooting (I think I've had it off a dozen times now and could do the job blindfolded :lol: ) that I started to get a bit lazy and reuse a gasket that had only been on a few weeks but later... but later realised that may be introducing new problems so relented and started using a new gasket each time...
As for the sparks, I fitted some Denso Iridium plugs a couple of years ago (but only about 25k miles), so they ought to be good for a little while longer. They were still in great nick when I checked them last summer (and cleaned the oil dribbles out of the plug wells), and as they made a huge improvement when I changed them I'm unwilling to switch to anything else. I've come across people who swear by Bosch plugs in the ES9J4, and those who swear by NGK (strangely nobody rooting for Champion though), so whilst they're not giving me problems I'll leave them well alone. They're not the worst job in the world to do, on the off-chance I end up keeping the car.
Fair enough - I've had three different plug types in this engine - it came with NGK BKR6EIX fitted which are a pretty standard, cheap single earth electrode type. They seemed ok but they did tend to foul if I did lots of short trips, which unfortunately I do. If you did mainly long trips they were probably fine.

I then changed them to Bosch FR7DC+ bought from GSF - they are also a cheap single electrode type and were even worse - within a month the insulators were completely fouled (particularly the rear three whose insulators were black) to the point where they were causing misfiring. To be honest I didn't know much about the spec's of spark plugs at the time and only had a vague understanding of heat ranges for spark plugs etc. When I did a bit of reading I realised that both these plugs were one heat range colder than the factory specified type - combined with lots of short trips they were fouling.

So next I fitted Bosch FR8KDC which is one of the two factory specified types, dual electrode and a heat range hotter than the other two types - no problems at all with them. I took them back out after about 3-4 months and the insulators were absolutely clean, white and pristine looking despite short trips where the car doesn't get a chance to warm up. The FR7DC+ I later found is designed more for LPG running in this engine not petrol. #-o So I would say getting the heat range right is probably more important than fancy tip materials.
I agree on the mixture issue - I probably ought to change it as the lambda sensor is the only in-flow sensor I haven't changed within the last 12-18 months (the non in-flow one being the knock sensor), but I've got to admit I find the workings of one a little bit hocus-pocus compared to any of the others. Mine is the original factory one, so quite possibly past its best by now.
What's hocus pocus about it ? :-D I think I have a pretty good understanding of how they work now, what is it you're not sure about ?
I've tried to undo it from the exhaust in the past to clean it up, but it's seized solid. As I'm now dependent on the car for work I'll be leaving it well alone to avoid any breakages that'll leave the car off the road. For the record I've replaced two steering racks, exhaust, front subframe, clutch and a multitude of other items in the vicinity of the lambda sensor, so I've tried shifting it quite a few times, and from all angles - it just refuses to budge.
Fair enough - as RichardW will attest getting the original oxygen sensor out of my car was a real challenge.

We had a good solid oxygen sensor socket, a decent size breaker bar and a couple of extensions to get the breaker bar out into the wheel arch where it could swing freely and we couldn't budge it despite plenty of penetrating lubricant etc... the socket was just trying to round off the hex on the oxygen sensor. In the end the way we got it to let go was to cut the plug off the cable so we could slide a giant ring spanner over it - there is just enough room to do so and that was able to break it free. :) Of course cutting the plug off commits you to changing it...

By the way I'm still getting excellent performance since the magic key reset on Friday - no apparent drop off in performance yet. =D>

stevieb
Posts: 265
Joined: 03 Nov 2004, 21:14

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by stevieb »

Ah, good info on the plugs and the lambda sensor there Simon - I'll keep that all in mind if I need to make any changes to mine. As for the inlet manifold gasket, I have a photo somewhere of a used one compared with a new one - the difference in thickness is quite noticeable...

I'm glad to hear the performance has stayed constant with yours too - have you noticed any change in the mpg yet, or is it too early to say? I have certain stretches of road where I check the onboard computer's reading at a given speed - it seems to give me an accurate representation of the mpg, in particular showing up the extra juice being consumed when the performance has dropped...

Speaking of which, I may have got to the bottom of my latest unexplained drop in performance/mpg. I decided that as I'd cleaned up the fuel pump and fuse terminals that I ought to clean up the LT terminals on the coilpack in case they were grotty. The coilpack fitted is a secondhand one I bought some years ago and I'd always got improvements in performance/mpg every time I'd switched the packs over (sound familiar?) but at the last swap it definitely seemed this one was best. However, this one has two small cracks in the top of the body.... I'd sealed the cracks after leaving it on a radiator overnight to dry it all out, but the sealant has separated from the body and I can only assume moisture has crept back in...

I've re-fitted the factory coilpack for now and it'll be getting a test drive shortly, but as part of my clean-up of the LT terminals I decided to pull off the rubber boots from both packs and see what the contacts looked like in that area - I know it's HT and should be less susceptible to a little bit of tarnishing, but hey, it all counts. The springs inside the boots weren't too bad, just a little dull, but one of them on each pack was distorted (coils compressed inside coils) and this may have been struggling to create a secure contact with the plug. The only other area of concern was the contacts in the bottom of the coilpack, where the springs meet it. These were badly tarnished on both packs, with no shiny spots where contacts touched, so I gave these a good scrub out with needle files and cotton buds. The test drive will tell me if it's helped in any way, but it can't have hurt.

I shall report back after my short jaunt to sunny Rotherham - it's a good mix of 70mph dual carriageway and some suburbs/town driving, so ideal for showing up any problems or changes.

User avatar
Mandrake
Posts: 8275
Joined: 10 Apr 2005, 17:23
x 355

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

stevieb wrote: I'm glad to hear the performance has stayed constant with yours too - have you noticed any change in the mpg yet, or is it too early to say? I have certain stretches of road where I check the onboard computer's reading at a given speed - it seems to give me an accurate representation of the mpg, in particular showing up the extra juice being consumed when the performance has dropped...
Unfortunately there is no mileage computer on the Xantia (not even as an option) so I can't directly track changes like you can. I also do a lot of very short trips during the week (the car doesn't even warm up) so I can only hit about 20mpg average under those conditions. So I'm judging it solely by subjective performance and responsiveness.
Speaking of which, I may have got to the bottom of my latest unexplained drop in performance/mpg. I decided that as I'd cleaned up the fuel pump and fuse terminals that I ought to clean up the LT terminals on the coilpack in case they were grotty. The coilpack fitted is a secondhand one I bought some years ago and I'd always got improvements in performance/mpg every time I'd switched the packs over (sound familiar?) but at the last swap it definitely seemed this one was best. However, this one has two small cracks in the top of the body.... I'd sealed the cracks after leaving it on a radiator overnight to dry it all out, but the sealant has separated from the body and I can only assume moisture has crept back in...
The best thing to seal the cracks in the coil pack housing is probably a hard setting two part epoxy glue, although I haven't tried it myself. I have three coil packs, :lol: the original, which has a number of large cracks, a new one I found on ebay for £75 a year ago (currently fitted) which has no cracks, and a second hand one which has one crack but otherwise looks in good order.

It's hard to be certain but in hindsight I don't think there is anything wrong with any of the coil packs. #-o I think swapping the coil packs was simply disturbing the faulty HT leads thus I was getting a temporary improvement each time I swapped them over. Because its running so nicely now (and the weather is miserable) I'm not willing to swap them over again to prove the point, I'm happy to leave the newest best looking coil pack in and call it a day. I paid for the coil pack so I might as well leave it in!
I've re-fitted the factory coilpack for now and it'll be getting a test drive shortly, but as part of my clean-up of the LT terminals I decided to pull off the rubber boots from both packs and see what the contacts looked like in that area - I know it's HT and should be less susceptible to a little bit of tarnishing, but hey, it all counts. The springs inside the boots weren't too bad, just a little dull, but one of them on each pack was distorted (coils compressed inside coils) and this may have been struggling to create a secure contact with the plug. The only other area of concern was the contacts in the bottom of the coilpack, where the springs meet it. These were badly tarnished on both packs, with no shiny spots where contacts touched, so I gave these a good scrub out with needle files and cotton buds. The test drive will tell me if it's helped in any way, but it can't have hurt.

I shall report back after my short jaunt to sunny Rotherham - it's a good mix of 70mph dual carriageway and some suburbs/town driving, so ideal for showing up any problems or changes.
I've had to replace one of the spark plug boots - from memory it was on cylinder number 1 (front right looking at the engine) as the rubber was swollen and no longer a snug fit on the spark plug insulator. Needless to say the boots need to be a snug fit, absolutely clean and free of oil/dirt contamination and as you say the spring needs to actually touch the spark plug electrode for best contact. In theory it should jump a small gap but that could lead to burning of the rubber and eventual carbon tracking.

PS is your car an auto or manual ?

stevieb
Posts: 265
Joined: 03 Nov 2004, 21:14

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by stevieb »

Mandrake wrote:
stevieb wrote:PS is your car an auto or manual ?
Mine's manual, which helps me suss out power/mpg issues with the onboard computer. I rarely see anything as low as 20mpg though (apart from booting it, ahem). Just recently I was getting mid-30's mpg over 1000 mixed miles which isn't bad for the 3-litre monster. Mid-40's is easily achievable on long 70mph journeys =D> The mpg improved the most after I'd had the Terraclean treatment last year - that made a HUGE difference.

I'd love to recommend a few tests you could do for comparison's sake, but the lack of an onboard computer hampers things, nevermind the silkiness of the auto box hiding other tell-tale signs. In mine I've found that backing right off the throttle on a downhill stretch of road, engine braking and using the footbrake if need be to maintain speed, should see my real-time mpg climb quickly - a steep downhill road with a drop down to 4th usually sees 999.9mpg showing on the display within two or three seconds. However, when it's misbehaving the engine braking effect is a lot stronger and louder (this effect is also directly proportional to the extent of the problem) and that magical 999.9mpg takes a lot longer to reach, if it even manages it. It's a long-winded thing to describe, but an instant giveaway that there's a problem...

Following up today's test-runs I can confirm the problem has to be ignition-related. My trip to Rotherham, straight after the installation of the factory-fit coilpack was smooth, refined, and VERY quiet (I have a stainless exhaust which isn't very forgiving when the engine is making unwanted noises). It was a huge improvement over this morning's trip out. I also managed the magical 50+mpg @ 50mph on the flat which is the sign that things are healthy. However, my return journey was a little louder and less refined - only slightly, but noticeable - so although this evening's journeys haven't shown much more deterioration I'm expecting it to hit me in the next few days, especially as I've regained the 2500-3000rpm drone :(

Either the disturbance of the ignition leads created a temporary cure (I'm unsure about this one, as right now my leads are all tightly bound with insulating tape and cable-tied away from the sources of earthing, at least in the areas I'd disturbed - unless of course the core is breaking down), or both my coilpacks are past their best and the problems are being revealed by the harsh engine bay environment. The engine runs better after cold starts than warm(er) starts which would reinforce this theory, and I've read online about electrical coils of various sorts suffering in hot environments, so maybe, just maybe...

Now, do I stump up for a brand new coilpack and leads which should solve the problem, or just the leads...? Hmmm...

User avatar
Mandrake
Posts: 8275
Joined: 10 Apr 2005, 17:23
x 355

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

stevieb wrote:
Mandrake wrote:
stevieb wrote:PS is your car an auto or manual ?
Mine's manual, which helps me suss out power/mpg issues with the onboard computer. I rarely see anything as low as 20mpg though (apart from booting it, ahem). Just recently I was getting mid-30's mpg over 1000 mixed miles which isn't bad for the 3-litre monster. Mid-40's is easily achievable on long 70mph journeys =D> The mpg improved the most after I'd had the Terraclean treatment last year - that made a HUGE difference.
Lucky bugger. I wish mine was a manual... :twisted:

The highest I've seen was 32.8Mpg on an 800 mile holiday trip with 4 people and luggage, but that was back before I had the first symptoms of trouble. On high octane petrol doing mixed driving but mostly 30mph I was seeing up to 23mpg for a while but now I'm back to really short (3 minute) trips again during the week it has dropped to 20mpg.
I'd love to recommend a few tests you could do for comparison's sake, but the lack of an onboard computer hampers things, nevermind the silkiness of the auto box hiding other tell-tale signs.
It's a shame they never fitted a trip computer on the Xantia - I've been told that the trip computer from a 406 V6 (D8) can be fitted to the Xantia relatively easy - just finding somewhere to mount it and running a few wires including one to the engine ECU - the code is still in the ECU to drive the missing trip computer but the wire is missing in the wiring loom.

I don't know about silkiness - the torque converter clutch on my gearbox is pretty worn so although gear changes are fine the transition from unlocked to locked is not exactly the smoothest sometimes. This manifests particularly when you're coasting at slow speeds - the gearbox will often unlock the torque converter to let the engine idle while coasting to reduce engine braking, when you put your foot down suddenly it tries to lock up quickly but with a slight delay then a bit of a jolt. Can't do much about it - I thought the gearbox was on deaths door nearly 5000 miles ago but after a few oil changes and some lubegard it is still going and apart from the torque converter lock up being a bit abrupt sometimes it still seems to be working ok - no clutch slip of the gears or other misbehaviour even under full acceleration, so any extra mileage it does is a bonus.

The auto adaptive gearbox really does muddy the waters though when trying to judge the engine performance, because both the gear change thresholds and the torque converter lock-up strategies change with both gearbox temperature and driving style, and whether the torque converter is locked or unlocked makes a big difference to the apparent performance and responsiveness of the engine.

For example it tends to stay unlocked a lot when the gearbox is really cold to warm it up quickly, (especially the first few minutes) for mid temperatures it has a mixed locked/unlocked strategy and over about 105 degrees it starts to strongly favour lock up - so after a really long spirited drive with a hot gearbox it will tend to keep the torque converter locked up even when you're down at 1200-1500 rpm pulling up a hill in 3rd for example which can curtail low rpm pickup a lot compared to it being unlocked. These variations in behaviour make it hard to judge performance.

What is really obvious though is lock up behaviour in 2nd gear when the engine performs well and when it doesn't. When accelerating through first and second it will start off unlocked but if your driving speed keeps you in 2nd gear with moderate acceleration and rpm for more than 2-3 seconds it will start transitioning from open to lock up.

When this happens the torque converter lock up places a lot more load on the engine - by trying to reduce the slip you're trying to accelerate the car but at the same time the reduced slip reduces the torque multiplication effect, hence it places a lot more torque load on the engine. When this happens there are two possibilities - the engine rpm holds steady and the car accelerates as the converter locks up, or the car stays at the same speed and the engine rpm sags.

When the engine is running badly (poor low rpm torque) as the converter locks up the car doesn't accelerate any faster and the engine revs just sag like its a cream pudding driving the car not a V6 :lol: You can clearly see the speedo staying the same and the rpm dropping 500 rpm or so.

When the engine is running well the reverse happens - as it transitions to lock up the engine revs stay roughly constant or increase slightly while the speedo shows the car accelerating rapidly, once the lock up transition is completed acceleration continues but engine rpm starts rising as well.

I can always tell by the performance in 2nd gear during torque converter lock up transition whether things are well or not.
In mine I've found that backing right off the throttle on a downhill stretch of road, engine braking and using the footbrake if need be to maintain speed, should see my real-time mpg climb quickly - a steep downhill road with a drop down to 4th usually sees 999.9mpg showing on the display within two or three seconds. However, when it's misbehaving the engine braking effect is a lot stronger and louder (this effect is also directly proportional to the extent of the problem) and that magical 999.9mpg takes a lot longer to reach, if it even manages it. It's a long-winded thing to describe, but an instant giveaway that there's a problem...
The 999mpg reading will be because the injectors are being cut off completely. What rpm is the car doing at that point ? If the rpm is above 1400 rpm and the throttle is at idle the injectors will be cut off. As you slow down and the rpm drops to 1100 rpm injection will be re-instated, it will not be cut off again unless the rpm increases to 1400 with the throttle still at idle. A Lexia will also show whether the injectors are in coasting cut off mode or not.

What I've noticed on mine recently is that sometimes the injection cut-off is not working when coasting despite being well above 1400 rpm - usually this happens to me in 1st gear at 2000-3000 rpm when I'm slowing down with my foot right off the throttle, instead of coasting smoothly with engine breaking it will lurch back and forth a bit as if I'm tapping the throttle and the injection is cutting off and coming back on again - since I'm well above 1400 rpm I'm assuming that either it thinks I'm touching the throttle slightly (TPS zeroing not quite right) or perhaps the MAP sensor is showing a lower than normal vacuum making it think the throttle is open slightly. (I am suspicious of a slight vacuum leak somewhere on mine as the ICV is closed too far to get correct idle)
Following up today's test-runs I can confirm the problem has to be ignition-related. My trip to Rotherham, straight after the installation of the factory-fit coilpack was smooth, refined, and VERY quiet (I have a stainless exhaust which isn't very forgiving when the engine is making unwanted noises). It was a huge improvement over this morning's trip out. I also managed the magical 50+mpg @ 50mph on the flat which is the sign that things are healthy. However, my return journey was a little louder and less refined - only slightly, but noticeable - so although this evening's journeys haven't shown much more deterioration I'm expecting it to hit me in the next few days, especially as I've regained the 2500-3000rpm drone :(

Either the disturbance of the ignition leads created a temporary cure (I'm unsure about this one, as right now my leads are all tightly bound with insulating tape and cable-tied away from the sources of earthing, at least in the areas I'd disturbed - unless of course the core is breaking down), or both my coilpacks are past their best and the problems are being revealed by the harsh engine bay environment. The engine runs better after cold starts than warm(er) starts which would reinforce this theory, and I've read online about electrical coils of various sorts suffering in hot environments, so maybe, just maybe...

Now, do I stump up for a brand new coilpack and leads which should solve the problem, or just the leads...? Hmmm...
If you've already replaced the coil pack once, I wouldn't do it again, at least not without strong evidence. Some cracks can be cosmetic only. Are the cracks in the epoxy resin on the top side or just around the sides of the black casing near the bottom ?

If its a crack right across the yellow resin in the top I'd be suspicious of it, but a good bead of epoxy glue should in theory fix that. If its just a bit of cracking around the sides of the black housing its not necessarily a problem - only if the crack goes deep enough into the epoxy potting would it necessarily cause a problem. As cracked as the black casing is on my original coil pack the epoxy is fine and I don't think there is actually anything wrong with it...

It's also possible for heat to cause one of the windings to short inside the coil pack, but its hard to prove conclusively if that is happening, since lots of things in the engine bay are warming up. You could swap a cold coil pack into a hot engine (ruling out heating of other things in the engine) but if the ignition leads are dodgy just the act of swapping it will introduce additional variables.

The engine note "loudness" will change with both timing advance and misfiring. If the engine is down on power but unusually quiet and smooth when accelerating (doesn't sound throaty like a V6 at all) then it can mean the timing is retarded. If you unplug the knock sensor and go for a drive you'll see what I mean - the ECU will log a knock sensor fault and drop the timing back 6-10 degrees which results in a VERY quiet, smooth sounding and smooth running engine with very lacking performance.

On the other hand if the engine is down on power but louder and raspier (rougher) sounding than normal particularly under hard acceleration then that's a misfire. When mine was misfiring badly I was reluctant to rev it over 4000 as it just sounded so rough and raspy.

On the ES9J4 you have the added complication that its a waste spark system so SOME causes of ignition misfire will take out two cylinders at a time - two cylinders that are on opposite sides of the timing cycle, so while you'd get a massive power loss from a two cylinder misfire if they're opposite cylinders it wont be as rough and raspy sounding as a single cylinder misfire. (In theory. Hard to test!) Any primary side ignition fault is likely to take out a pair of cylinders, while spark plug leads will generally only affect the rear cylinders.

Given that you've already changed the coil pack once but not the leads, I would suggest you try the leads rather than spending any money on a new coil pack. The last set of leads I took out (which were less than a year old) looked absolutely perfect but there was something wrong with them, so just because they look ok doesn't mean they are - especially when they're factory originals, like yours. Spark plug leads do have a limited life. A set of leads is also 1/2 to 1/3 of the price of a coil pack.

If you do change the leads be very careful fitting them, its easy to snag the insulation on the teeth in the guides and I managed to damage one set by doing so.

Engine still performing perfectly by the way! :) That's nearly a week with no change now, even with a dodgy oxygen sensor.

stevieb
Posts: 265
Joined: 03 Nov 2004, 21:14

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by stevieb »

That's all interesting reading regarding the auto box - I often wondered how it compared with the manual, and that describes it well. I like how you've found a tell-tale in the gearbox actions that shows up the engine behaviour too... :)
Mandrake wrote:The 999mpg reading will be because the injectors are being cut off completely. What rpm is the car doing at that point ? If the rpm is above 1400 rpm and the throttle is at idle the injectors will be cut off. As you slow down and the rpm drops to 1100 rpm injection will be re-instated, it will not be cut off again unless the rpm increases to 1400 with the throttle still at idle. A Lexia will also show whether the injectors are in coasting cut off mode or not.

What I've noticed on mine recently is that sometimes the injection cut-off is not working when coasting despite being well above 1400 rpm - usually this happens to me in 1st gear at 2000-3000 rpm when I'm slowing down with my foot right off the throttle, instead of coasting smoothly with engine breaking it will lurch back and forth a bit as if I'm tapping the throttle and the injection is cutting off and coming back on again - since I'm well above 1400 rpm I'm assuming that either it thinks I'm touching the throttle slightly (TPS zeroing not quite right) or perhaps the MAP sensor is showing a lower than normal vacuum making it think the throttle is open slightly. (I am suspicious of a slight vacuum leak somewhere on mine as the ICV is closed too far to get correct idle)
I can comfortably drop to 1100rpm and see 999.9mpg, but this is usually after a gradual slow-down (national speed limit down to 30mph usually) so the 1400rpm threshold may reduce if engine braking happens for more than a given period of time. I've found that even at 2500rpm, it's almost impossible to get the magic 999.9mpg on the display in first or second, so I guess road speed must have a bearing on whether the injectors are allowed to close - you're more likely to need a sudden surge of torque to get you going again at 20mph than at 60mph - makes sense. I think I cured all of my vacuum leaks last summer after working methodically round the various potential causes. One surprising culprit was the little L-shaped rubber hose linking the ICV with the inlet manifold - my old one had split in the crease of the L and was seeping air in whenever the ICV closed. A new one was only a couple of quid from the main stealer, so I didn't hesitate in replacing it.

Mandrake wrote:If you've already replaced the coil pack once, I wouldn't do it again, at least not without strong evidence. Some cracks can be cosmetic only. Are the cracks in the epoxy resin on the top side or just around the sides of the black casing near the bottom ?

If its a crack right across the yellow resin in the top I'd be suspicious of it, but a good bead of epoxy glue should in theory fix that. If its just a bit of cracking around the sides of the black housing its not necessarily a problem - only if the crack goes deep enough into the epoxy potting would it necessarily cause a problem. As cracked as the black casing is on my original coil pack the epoxy is fine and I don't think there is actually anything wrong with it...

It's also possible for heat to cause one of the windings to short inside the coil pack, but its hard to prove conclusively if that is happening, since lots of things in the engine bay are warming up. You could swap a cold coil pack into a hot engine (ruling out heating of other things in the engine) but if the ignition leads are dodgy just the act of swapping it will introduce additional variables.

The engine note "loudness" will change with both timing advance and misfiring. If the engine is down on power but unusually quiet and smooth when accelerating (doesn't sound throaty like a V6 at all) then it can mean the timing is retarded. If you unplug the knock sensor and go for a drive you'll see what I mean - the ECU will log a knock sensor fault and drop the timing back 6-10 degrees which results in a VERY quiet, smooth sounding and smooth running engine with very lacking performance.

On the other hand if the engine is down on power but louder and raspier (rougher) sounding than normal particularly under hard acceleration then that's a misfire. When mine was misfiring badly I was reluctant to rev it over 4000 as it just sounded so rough and raspy.

On the ES9J4 you have the added complication that its a waste spark system so SOME causes of ignition misfire will take out two cylinders at a time - two cylinders that are on opposite sides of the timing cycle, so while you'd get a massive power loss from a two cylinder misfire if they're opposite cylinders it wont be as rough and raspy sounding as a single cylinder misfire. (In theory. Hard to test!) Any primary side ignition fault is likely to take out a pair of cylinders, while spark plug leads will generally only affect the rear cylinders.

Given that you've already changed the coil pack once but not the leads, I would suggest you try the leads rather than spending any money on a new coil pack. The last set of leads I took out (which were less than a year old) looked absolutely perfect but there was something wrong with them, so just because they look ok doesn't mean they are - especially when they're factory originals, like yours. Spark plug leads do have a limited life. A set of leads is also 1/2 to 1/3 of the price of a coil pack.

If you do change the leads be very careful fitting them, its easy to snag the insulation on the teeth in the guides and I managed to damage one set by doing so.

Engine still performing perfectly by the way! :) That's nearly a week with no change now, even with a dodgy oxygen sensor.
Glad to hear the ICV reset-wotsit is still showing benefits. I asked others on the Coupé Club to try it and report back whether they felt any difference, but nobody bothered so I never got to find out whether I was imagining it - for a while there I wondered if I was losing the plot... :roll:

As for the coilpack I'm divided on that one, but will probably go for the HT lead option first, just for peace of mind because I know the insulation on a couple of mine has been damaged in a few places. My doubts about the coilpack stem from the switch from the original one to the secondhand replacement one (at around 70k miles) where the improvement in performance was incredible. But since then I've had very long and drawn-out drops in power and swapping them back and forth sees that performance increase each time, but followed by that gradual drop again over time - it just reminds me of taking batteries out of the TV remote thinking they're flat, and them then working fine when you pop them back in ten minutes later after they've had a rest. Daft I know, but... I guess a change of leads will prove the point one way or the other...

I nearly forgot the update for the day - I've done Sheffield to Derby and back this morning and the car's still running pretty well, with just odd moments where it feels flat. One thing I've noted this week is on those sunken bits of motorway at 70mph - the ones where the car goes light for a split-second then comes down heavy - the power changes slightly in those moments and sometimes doesn't return to its previous state - whether this is HT leads moving about and changing things or whether this is a problem with the fuel pump/pressure I don't know. Time will tell, no doubt...

User avatar
Mandrake
Posts: 8275
Joined: 10 Apr 2005, 17:23
x 355

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

stevieb wrote: I can comfortably drop to 1100rpm and see 999.9mpg, but this is usually after a gradual slow-down (national speed limit down to 30mph usually) so the 1400rpm threshold may reduce if engine braking happens for more than a given period of time. I've found that even at 2500rpm, it's almost impossible to get the magic 999.9mpg on the display in first or second, so I guess road speed must have a bearing on whether the injectors are allowed to close - you're more likely to need a sudden surge of torque to get you going again at 20mph than at 60mph - makes sense. I think I cured all of my vacuum leaks last summer after working methodically round the various potential causes. One surprising culprit was the little L-shaped rubber hose linking the ICV with the inlet manifold - my old one had split in the crease of the L and was seeping air in whenever the ICV closed. A new one was only a couple of quid from the main stealer, so I didn't hesitate in replacing it.
The docs I have don't mention any dependence on road speed for the injection cut-off, but the engine ECU does receive a road speed signal, at least on the Automatic. Not sure where it gets it from though - whether from the gearbox ECU or whether it taps into the signal to the electronic speedo.

With the 1400 and 1100 rpm thresholds all that means is you have to be above 1400 rpm at the time you take your foot off the pedal for the injectors to cut off. Once they've cut out they will remain cut off until you drop to 1100 rpm at which point they will activate again. Once that happens you would have to speed up to 1400 rpm again before taking your foot off to get them to cut off. Taking your foot off between 1100 and 1400 will not cut off the injectors, only maintain it if they were already cut off above 1400.
Glad to hear the ICV reset-wotsit is still showing benefits. I asked others on the Coupé Club to try it and report back whether they felt any difference, but nobody bothered so I never got to find out whether I was imagining it - for a while there I wondered if I was losing the plot... :roll:
Don't worry, more than a few posters in this thread think I lost the plot dozens of pages ago :-D All I can say is that the problems are real, just that the intermittent nature of them makes it incredibly difficult to troubleshoot, and I'm confident that I was dealing with two simultaneous intermittent problems for a long time as well.

I may have spoken too soon about the ICV reset - the car ran like a rocket right up until Friday night (eg a whole week) - started it up on Saturday, drove off, performance was immediately sluggish. #-o

So what was different between Friday and Saturday ? During the week it gets started at 8am when its quite cold, and because I'm aware of the issue with the oxygen sensor not warming up at idle (and the ECU starting to use the data despite this) I deliberately drive off quite quickly after starting (about 20 seconds) so that the oxygen sensor doesn't linger in a partially warmed up state feeding bad data to the ECU - the gearbox already holds the revs higher in 1st gear during the first two minutes of driving on a cold start so I imagine that gets the oxygen sensor hot fairly quickly.

On Saturday I started it after lunch time and while we were mucking around sorting out the address we were going to it probably idled 2-3 minutes before departing. Difference number two is that Friday had been very dry while Saturday was absolutely bucketing down, the air was damp, the road was throwing up water spray everywhere etc...(to be fair though there had been a couple of wet days earlier in the week that didn't seem to affect it, although not nearly as wet)

Three times while we were out I pulled over, switched it off for a minute or two then tried the "ICV reset" with the key - no improvement whatsoever. This was on a hot engine mind you. The fourth time we pulled into an ASDA and left it parked for 20 minutes or so while we went inside, when we came out I tried the reset one more time and this time it had quite a big effect, (either that or co-incidence) so it seems like the "ICV reset" does nothing if the key hasn't been turned off for at least 20 minutes or so ?

I was also quite low on petrol on Saturday so on Sunday I filled it up - a fresh tank of petrol, a little injector cleaner and an "ICV reset" and its back to full power once again... 8-[

For a couple of months I had been putting a dose of injector cleaner in with each fill up (already high octane shell v-power) and the performance had stayed really good, after two tanks of petrol with no injector cleaner the performance trailed off again, then when I went back to adding it it went up again. Anyone have any ideas why ?

There is definitely still something fishy going on, I think the next step is to get this suspect oxygen sensor which I know doesn't warm up properly replaced with the correct part and take things from there. I'm going to get the one from Lambda Power - after emailing back and forth with the guy a number of times I'm happy about the diagnosis of the oxygen sensor not being the right one and also happy that he can supply the correct one. Probably won't be for a month or two though as the weather won't be up to fitting it for a while.
As for the coilpack I'm divided on that one, but will probably go for the HT lead option first, just for peace of mind because I know the insulation on a couple of mine has been damaged in a few places.
Damaged in what way ? Even though there's two layers (an inner white layer, maybe teflon, and an outer black layer) I found with the set I damaged that I just nicked the black layer - no damage to the inner white layer and it was flashing over through the nick in the insulation to the rocker cover - I taped it up with 3M self amalgamating tape and that cured it for about 2 weeks but eventually the spark melted through the tape! The coils in this coil pack can produce up to 60kV and most insulation tape simply can't handle that, not even the 3M stuff. (Well it can for a while, but the heat degrades it)
My doubts about the coilpack stem from the switch from the original one to the secondhand replacement one (at around 70k miles) where the improvement in performance was incredible. But since then I've had very long and drawn-out drops in power and swapping them back and forth sees that performance increase each time, but followed by that gradual drop again over time - it just reminds me of taking batteries out of the TV remote thinking they're flat, and them then working fine when you pop them back in ten minutes later after they've had a rest. Daft I know, but... I guess a change of leads will prove the point one way or the other...

I nearly forgot the update for the day - I've done Sheffield to Derby and back this morning and the car's still running pretty well, with just odd moments where it feels flat. One thing I've noted this week is on those sunken bits of motorway at 70mph - the ones where the car goes light for a split-second then comes down heavy - the power changes slightly in those moments and sometimes doesn't return to its previous state - whether this is HT leads moving about and changing things or whether this is a problem with the fuel pump/pressure I don't know. Time will tell, no doubt...
Interesting observation on the change in performance over a sudden dip - clearly something under the bonnet is moving, but it could be anything really.

I've sometimes wondered whether there could be a fault in the wiring loom where it crosses through the black channel just behind the coil pack - most jobs in the area will tend to disturb this wiring...I've done continuity tests to the various sensors including the knock sensor and everything checks fine even when I wiggle the harness around, but I can't get away from the nagging feeling that some wiring somewhere in the engine wiring loom is not reliable...

stevieb
Posts: 265
Joined: 03 Nov 2004, 21:14

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by stevieb »

It sounds like you're experiencing the same warm-engine/damp-weather issues I'm suffering. Mine has mostly been behaving, with no signs of the mis-fire returning, but warm starts are seeing heavy fuel consumption and a slightly heavy feel to the car for short periods, regardless of the atmospheric conditions. It clears after a few miles (quicker if it gets a bit of a boot) so it might be the oxygen sensor on mine struggling - the sensor cooling quicker than the engine sensors whilst the car is stood and then not getting back up to temp quick enough with an un-choked engine... Maybe... I've certainly suspected that setting off quickly helps things, but in my case I think turning the key straight to 'start' is better than the old diesel driver's habit of turning it to position II and waiting for the lights to go out...

As for my HT leads, it's the black outer insulation on mine that's been split. It's only along the plastic guide for the leads, so hopefully that'll stop the spark taking a shorter route, but I don't know. I DO know that the old test of checking it in complete darkness doesn't show any jumping sparks anywhere. I'll probably get some HT leads in due course, but I'm holding onto my limited funds right now on the off-chance it's something else that's at fault. I don't especially want to double-up on any work in the engine bay at this time of the year either - it's too damned cold without a garage.

The V-Power cure sounds familiar too - I did exactly the same thing last year, and even did the additive trick - in my case a full bottle in a quarter tank, so a VERY strong mix. It made enough difference for me to invest in the Terraclean treatment for mine. It was worth it, and is a good reason for me to doubt my oxygen sensor is bad because this treatment works wonders. One other thing comes to mind with this though - my dad owned an auto 3.5 litre V8 Rover P5B back in the 80's, which was designed to run on 5-star fuel, not 4-star. On 4-star it would knock (they called it 'pinking' then), especially when caught in the wrong gear. He used a Redex octane booster added to regular 4-star leaded and it cured it.

My thought is that if our knock sensors were giving readings to the ECU that were artificially high, the ECU would retard the ignition and we'd feel it through power loss and increased fuel consumption, even if only temporarily. Using higher octane fuel (or an additive) might mask the effect by raising the threshold at which the engine knocks, to the point that V-Power is giving you the performance you should get from regular unleaded. It's only a theory, but...

The other thing to consider is that I read the ICV reset online as being for a 1.8 petrol - it's entirely possible it resets other things on the ES9J4 too, including certain fuel/ignition parameters, but we don't know what...

That makes sense about the rpm's affecting the downhill mpg - I could see that I often needed to keep revs up higher to get the 999.9mpg (low rpm in 5th at 30mph from flat to downhill never gave me any sudden rise in mpg, whereas dropping to 3rd then back to 5th would instigate it), but I'd never paid enough attention to work out what the trick was.

The issue on dips in the road may have been solved - I checked my tyre pressures and found they were all down around 26psi (they're all less than a year old and were last checked around 5 or 6 months ago - they should be 32-33psi - so where that's gone I don't know). Admittedly this was cold tyres, but after warming up on a long motorway run they still weren't reaching 30psi, so I've topped them up. The suspension set-up on the 406 is unnecessarily complicated, and I wonder if soft tyres were causing a weird wallowing effect that would take a while to settle. I've also wondered in the past whether the ECU detects changes in load (as much as it can do with its basic set of sensors), and this sudden extra load might cause it to change the fuelling in some way - unlikely, but it's the only way I could explain why the change sometimes stuck. Either way, the lower psi's will have been hitting my mpg so I'm looking forward to 40mpg tomorrow... :rofl2:

stevieb
Posts: 265
Joined: 03 Nov 2004, 21:14

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by stevieb »

I spoke too soon. Mine was noisy and sluggish again this morning. As I've said before, it's not down to the level it was when the fuel pump wasn't getting its volts, but my 50mph M1 roadworks test saw high 30s - low 40's mpg, the return of the 2-3000rpm drone and a delay in pick-up when squeezing the accelerator pedal. Strangely, towards the end of my 40-odd mile drive it cleared itself and reverted to normal.

I had some time to kill at this morning's appointment so I did the ICV reset, but saw no improvement on the way home as it had reverted to its 8am state. I stopped-off at services on the way back with no noticeable improvement, but a second stop-off at a mate's mum's place (now in full sunshine) saw it clear itself. This is harking back to my 'Invisible Caravan' thread on the Coupé Club where I found the exact opposite - the car ran well in the morning, but after being sat in the sun at work it would run like a dog. The only time it behaved on my way home would be on an overcast day...

It's funny how the weather is effecting us both like this. Now, where to check next...?

stevieb
Posts: 265
Joined: 03 Nov 2004, 21:14

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by stevieb »

Another update you might be able to help me with Simon.

I've been through a few more engine bay connectors and earthing points to clean them up and re-mount them - none of them were particularly bad. Then I decided to start the car and see if it ran loud or quiet (and take the opportunity to wiggle the now loose HT leads and see if that made a difference - it didn't). The engine is running noisy, from a cold start, with a return of the top-end clatter/tapping noise I'd had until last summer.

It's almost diesel-like at the minute and quite disturbing. It emanates from beneath the forward area of the inlet manifold so it's got to be either a rear-bank injector or just plain old noisy tappets. I'd always assumed it was a noisy injector seeing as the tappets are hydraulic and shouldn't be noisy, and considering the Terraclean treatment seemed to cure this noise I thought I'd guessed right. I have a spare set of injectors and I think I'm going to have to take the plunge and fit them - or at least the rear three to see what happens...

Now I get to ask for some help - my ICV hums loudly (so much so I can hear it in the cabin) with the ignition in position II and the engine off. It sounds a lot like it's jammed up against its stop and can't move any further - like a stalled motor - but considering the physical stops inside the barrel of the ICV are beyond the normal operating arc of the inner valve it sounds as if it's being asked to rotate to a position it can't achieve. I noted with the problems I had last summer that this excess noise was a warning that something somewhere was amiss, because some days it was virtually silent and all was well. If yours is still behaving Simon, would you mind telling me if yours hums as well, ideally with a cold engine? And secondly, with the engine running, can you hear the air passing through the ICV? I have a soft hissing sound from that area that might be an air leak, but I think may just be the airflow being strangled a bit too much - it'd be nice to identify which it is.

EDIT: This was my Coupé Club thread about dismantling an old ICV - http://www.406coupeclub.org/PHPBB3/view ... 83&t=44110" onclick="window.open(this.href);return false; - I'd forgotten just how much metal swarf was stuck to the grease under the plastic cap, not to mention what was stuck to the magnets. This can't be doing it any good, can it? :evil:

User avatar
Mandrake
Posts: 8275
Joined: 10 Apr 2005, 17:23
x 355

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

stevieb wrote: As for my HT leads, it's the black outer insulation on mine that's been split. It's only along the plastic guide for the leads, so hopefully that'll stop the spark taking a shorter route, but I don't know.
If you mean the front plastic guides near the coil pack, that's exactly where the insulation of mine was punctured:

Image

The tiny little hole near the letter R on the middle cable was causing a flash over through the hole in the plastic guide to the rocker cover top. What's more it was only causing an under load misfire - at idle there was no misfire because the spark voltage is much lower - open the throttle and the required spark voltage increases to the point where its easier for the spark to jump to the chassis than at the spark plug electrode.

I know for sure it was jumping there because I taped the wire up with self amalgamating tape which cured the misfire for two weeks, when the misfire returned I found this:

Image

The spark had actually flashed through the insulation, melting a hole in it. :)
The V-Power cure sounds familiar too - I did exactly the same thing last year, and even did the additive trick - in my case a full bottle in a quarter tank, so a VERY strong mix.

[...]

My thought is that if our knock sensors were giving readings to the ECU that were artificially high, the ECU would retard the ignition and we'd feel it through power loss and increased fuel consumption, even if only temporarily. Using higher octane fuel (or an additive) might mask the effect by raising the threshold at which the engine knocks, to the point that V-Power is giving you the performance you should get from regular unleaded. It's only a theory, but...
I've thought along very similar lines to you over the last few months - the percentage of time where the engine runs poorly is greatly reduced (almost eliminated) by running on high octane (99 or 97) fuel with some injector cleaner, (which probably also boosts the octane even further since its basically kerosene ??) however I believe that this is masking the true cause as the first 6 months I had the car I only used 95 octane and didn't have any problems.

I'm pretty sure now that the intermittent power loss I've seen over the last year has been a combination of conventional misfiring, (in my case ignition related, especially under wide throttle) and knock sensor related timing retard. (loss of low rpm torque/pickup)

The misfire was affected by dampness and didn't respond to battery off ECU resets, while the retarded timing does temporarily respond to an ECU reset, as if the ECU maps get "corrupted" over time.

What I've never been able to determine is why the timing gets retarded - I know for certain now that its not a faulty ECU (I'm now running on another ECU) so it must be an actual signal on the knock sensor input to the ECU triggering it.

It could be a "false" knock signal due to electrical interference from to a broken wire or faulty earthing to the knock sensor, a faulty/intermittent knock sensor, (I've heard of knock sensor bolts coming loose causing the sensor to rattle!) it could be excessive mechanical noise from the engine. (noisy hydraulic lifters, other metallic noises in the engine due to wear or damage)

Or the knock sensor could be detecting genuine engine knock under circumstances where it shouldn't normally happen - I need to do a bit more reading but I believe that a lean mixture can knock more easily for a given octane and timing advance so if one cylinder was running a bit lean (maybe an inlet runner air leak, or a slightly blocked injector) on the verge of misfiring it may knock under load especially at low rpm - the knock sensor detects this knocking and the timing of ALL the cylinders is retarded until the knocking stops - result is a massive power loss at low rpm. (This ECU is not smart enough to adjust the knock retard individually per cylinder as far as I know - some more advanced ECU's can)

The knock detection algorithms are quick to retard the timing but slow to re-advance it, especially if it knocks consistently enough to cause a lower octane map to be selected. Once that happens it can take a lot of driving with no knocking detected for a high octane map to be re-selected - or an ECU reset... ;)

If the knocking is intermittent but frequent enough the ECU may end up stuck in a low octane map after a while.

So far I can't figure out how to identify what is triggering knock retard and whether its real knock, mechanical noise or an electrical problem - especially when the ECU doesn't provide any diagnostic information regarding the knock sensor activity or the amount of knock retard that is being applied. :?
The other thing to consider is that I read the ICV reset online as being for a 1.8 petrol - it's entirely possible it resets other things on the ES9J4 too, including certain fuel/ignition parameters, but we don't know what...
If only we could get a bit more "inside information" on the MP7.0... I've looked pretty hard and there is very little information on its programming. What I have found so far I've pieced together from multiple sources plus some empirical testing of my own...
Last edited by Mandrake on 04 Feb 2014, 20:23, edited 2 times in total.

Hell Razor5543
NOT Alistair or Simon
Posts: 11465
Joined: 01 Apr 2012, 09:47
x 1285

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Hell Razor5543 »

If ever you have to insulate a high voltage cable you might want to try using PTFE tape as an under layer first. IIRC it has an electrical resistance higher than air. I know (from a friends' tests) that it can handle at least 50,000 volts (but I don't know at what amperage).

stevieb
Posts: 265
Joined: 03 Nov 2004, 21:14

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by stevieb »

Mandrake wrote:It could be a "false" knock signal due to electrical interference from to a broken wire or faulty earthing to the knock sensor, a faulty/intermittent knock sensor, (I've heard of knock sensor bolts coming loose causing the sensor to rattle!) it could be excessive mechanical noise from the engine. (noisy hydraulic lifters, other metallic noises in the engine due to wear or damage)

Or the knock sensor could be detecting genuine engine knock under circumstances where it shouldn't normally happen - I need to do a bit more reading but I believe that a lean mixture can knock more easily for a given octane and timing advance so if one cylinder was running a bit lean (maybe an inlet runner air leak, or a slightly blocked injector) on the verge of misfiring it may knock under load especially at low rpm - the knock sensor detects this knocking and the timing of ALL the cylinders is retarded until the knocking stops - result is a massive power loss at low rpm. (This ECU is not smart enough to adjust the knock retard individually per cylinder as far as I know - some more advanced ECU's can)

The knock detection algorithms are quick to retard the timing but slow to re-advance it, especially if it knocks consistently enough to cause a lower octane map to be selected. Once that happens it can take a lot of driving with no knocking detected for a high octane map to be re-selected - or an ECU reset... ;)

If the knocking is intermittent but frequent enough the ECU may end up stuck in a low octane map after a while.

So far I can't figure out how to identify what is triggering knock retard and whether its real knock, mechanical noise or an electrical problem - especially when the ECU doesn't provide any diagnostic information regarding the knock sensor activity or the amount of knock retard that is being applied. :?
I've read the same thing about knock sensors coming loose. The annoying thing is that not only does the inlet manifold need to be removed to access it, but so does the plenum chamber, which means another set of gaskets and another risk of dropping something into the inlets. I did check mine the best I could the last time I had the manifold off, but it's difficult to tell. The fly-lead that feeds it is really flexible, so wiggling that about doesn't really help - if it was a bit stiffer you could probably feel whether the sensor was loose, but no chance. All you can do is wiggle it and listen for any movement.

You might've hit the nail on the head with the injector comment. Whether I've got injector or tappet noise it might well be creating the unwanted retardation via the knock sensor. I think I'll have a session at the weekend swapping the injectors front to back (I know my front ones are good, so there's no point putting unknown second-hand ones in the back) and see if the noise moves with the injectors. If it does, then I just need to swap the noisy one(s) with the spares until the noise goes. The front ones can at least be accessed without lifting the inlet manifold each time

stevieb
Posts: 265
Joined: 03 Nov 2004, 21:14

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by stevieb »

Hell Razor5543 wrote:If ever you have to insulate a high voltage cable you might want to try using PTFE tape as an under layer first. IIRC it has an electrical resistance higher than air. I know (from a friends' tests) that it can handle at least 50,000 volts (but I don't know at what amperage).
Good call HR =D>

I may just try this - I have a roll of PTFE in the garage gathering dust... If I try just the PTFE first it might at least eliminate the HT leads once and for all because I'm easily going to spot a scorch-mark on white tape if one should appear...

stevieb
Posts: 265
Joined: 03 Nov 2004, 21:14

Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by stevieb »

I don't know whether anybody has cut open one of the connectors on the HT leads (there may have been a pic earlier in the thread, but I'll be jiggered if I'm going through all 98 pages checking :rofl2: )

I've got to be honest, I'm not impressed with the quality.

Image

I've been looking at making my own for a while, but the plugs seem a bit difficult to get hold of, so it looks like it's Bougicord or nothing. Unfortunately.