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

[Stempy]

When I removed the injectors on my Xantia after 120k miles I didn't find anything in the meshes, in fact they looked almost good as new, perhaps down to always using quality fuel with the correct detergents etc.

[stevieb]

When I removed the injectors on my Xantia after 120k miles I didn't find anything in the meshes, in fact they looked almost good as new, perhaps down to always using quality fuel with the correct detergents etc.

Good call Stempy

I had a debate with a chap in a local parts factors a month or so ago about oil choices, when I was having bother trying to find some Total Quartz 9000 (Total petrol stations don't sell it - Quantum or Mobil 1, but not Total! ). His attitude was "if it's the right grade then it's fine" and tried to sell me 5 litres of Castrol. He wasn't taken with my attitude which is simple - Castrol stuff makes this car run like a dog, and has done in every Peugeot I've owned. Even their gearbox oil ruins the gearchange despite being the "correct grade". If you start looking into the small print and working out which oils have the PSA approval codes, you find there aren't many. There's got to be a reason for this. Interestingly, the very few PSA approved oils are also some of the few Porsche have approved too - interesting because of Porsche's involvement in the uprating of the ES9J4 to the ES9J4S.

With this experience of oils, I often wonder if PSA engines are as finicky about fuel and its additives too...

[lexi]

Probably a good choice of oil is the 5w40 fully synth. You should get slightly better mpg in colder weather as well as better cold start protection.
I have NGK platinum to put in VEL.
The advantage of fully synthetic is being able to stretch the grades. I mean 5w40 is a big jump. Mineral struggles to make 10w 40. In fact mineral performs better at close together weights ie 15 w 40 20w50. It just does not have quite the same protection at -15deg cold starts. Not that cold starts will kill an engine because of mineral oil, but there will be more friction.

Bear in mind guys. With these very thin oils in last generation design, you will lose oil pressure, as a gauge will show you. Hot conditions more so.
You still have the stickyness of the synthetic oil, coating your parts , but oil pressure may have an effect on some other things...........leaks for one
The synthetic is a bit rich for me. I feed mine 10w40 semi synth Ultratech. I have 40 litres still to use. Change it every 5k

[Mandrake]

When I removed the injectors on my Xantia after 120k miles I didn't find anything in the meshes, in fact they looked almost good as new, perhaps down to always using quality fuel with the correct detergents etc.

Could well be. Who knows what this car ran on before I got it, plus since months of supermarket fuel when I first got it...

I'm not necessarily expecting injector screens to be clogged up though, other problems could be varnish deposits in the pintle valve or maybe even intermittent seizing of the pintle shaft...or there could just be enough of a flow imbalance between injectors to make a cylinder run too lean with all the knock on effects from oxygen sensor feed back, knock sensor feedback etc.

There are no lifter/injector noises when the engine is cold and for the first few minutes of running, its very quiet as my video showed, but there are a couple of real clackers from the rear bank when it's hot - I'd always assumed it was noisy lifters that didn't respond to the oil treatment, but it now seems plausible that its a couple of injectors that get noisy when they're hot. (Hard to prove as you can't unplug a rear injector on a running engine)

The question is, does a noisy injector (especially one that only gets noisy when hot) necessarily mean a problem with fuel delivery ? I really don't know. I'm trying to picture what might cause an injector to go from nearly silent to noisy when it gets hot - about the only thing I can think of is there could be some varnish on the seat which quietens the movement but when it heats up the varnish goes soft ? Not sure.

It would be foolish of me not to pop the injectors out of the second hand rail I've bought and check the screens are clean and flush out the rail too - who knows where it's been, how long its sat, and what it's condition will be like. I'll do my best to set up a test rig so that I can do a pressure and balance test as well - I'd feel a lot happier putting in a set of injectors which just passed a balance test than a set in unknown condition.

Another possibility that occurs to me is an air leak around one of the injectors that changes intermittently - if one of the seals has split a small air leak there would cause a localised vacuum leak that would make that cylinder run lean and cause a mixture imbalance at lower throttle openings... and I do have a slight vacuum leak somewhere which I have not been able to locate... that's why I also want to remove the 2nd hand injectors from their rail to inspect the o-rings and fit them back again greased properly to ensure I won't be adding any air leaks.

[stevieb]

Simon, this is the offending crankcase breather you need to move when lifting the fuel rails out - you can see my heatshrink tubing fix is almost shrunk to size - I think a bit more sitting in traffic will finish off the job nicely:



As for spark plugs, I installed the front three on mine earlier - I debated whether to hold back on the job until I could do all six, then reasoned that if the engine ran worse with those three fitted I could at least return the spare three when I went to buy something different. My inlet manifold gaskets (I ordered two again) are due on Wednesday, so that's when the rear bank will get done.

Even with only half the job done, the engine sparked into life quicker and ran smoother right from the get-go. One thing I've been finding is that things start to sound a bit laboured as they get warm with the engine drone still appearing at just below 3,000rpm, with this being especially noticeable from a warm start. Well today was a warm start and it was a lot better (blipping the throttle was a LOT more responsive too), so I'm looking forward to seeing what Wednesday brings now

Btw, I plumped for the Denso Twin Tip plugs. I'll give a fair appraisal once I've got all six in.

[Mandrake]

Simon, this is the offending crankcase breather you need to move when lifting the fuel rails out - you can see my heatshrink tubing fix is almost shrunk to size - I think a bit more sitting in traffic will finish off the job nicely:

Thanks Steve,

I know that breather tube well - I've had it disconnected and pushed up out of the way a bit before, thankfully it hasn't broken on me! I will certainly treat it with care. Mind you my car is only coming up on 109k miles and I seem to recall you saying yours was approaching 200k ??! Twice the mileage would certainly make the plastics and rubber under the bonnet that much more brittle...

As for spark plugs, I installed the front three on mine earlier - I debated whether to hold back on the job until I could do all six, then reasoned that if the engine ran worse with those three fitted I could at least return the spare three when I went to buy something different. My inlet manifold gaskets (I ordered two again) are due on Wednesday, so that's when the rear bank will get done.

Even with only half the job done, the engine sparked into life quicker and ran smoother right from the get-go. One thing I've been finding is that things start to sound a bit laboured as they get warm with the engine drone still appearing at just below 3,000rpm, with this being especially noticeable from a warm start. Well today was a warm start and it was a lot better (blipping the throttle was a LOT more responsive too), so I'm looking forward to seeing what Wednesday brings now

So the engine drone increases when the engine is hot, but you've still not experienced any return of the invisible caravan ? It could be that your drone is your exhaust system, didn't you say you had a non-standard exhaust fitted ?

My original exhaust (whose rear silencer was all rust and no baffles) had a really loud drone/boom centred at 1500 rpm when I put my foot down but was relatively quiet higher up. The replacement exhaust system I fitted is quiet and boom free below 2000 rpm but now has a noticeable drone centred around 2500. Nothing too bad, but I do notice it on motorway cruising as its exactly the rpm I'm doing at 60-70mph. If I accelerate heavily at 2500 rpm it even sounds slightly raspy. I think its just the characteristic of the new exhaust system.

Btw, I plumped for the Denso Twin Tip plugs. I'll give a fair appraisal once I've got all six in.

Nice. I think any good quality plug will see some improvement if the gaps on the old plugs were excessive. Did you compare the gaps of old and new ?

During cranking the spark is a lot weaker than idle due to lower battery voltage limiting the coil primary current, so I think the health of the whole ignition system including plugs has quite an effect on how quickly it "catches" when cranking.

In my case I noticed a difference in starting when swapping the ECU - my original ECU always took about half a second of cranking before it would fire regardless of plugs, the one in the car now causes it to catch and fire instantly on the first revolution. My guess is that this ECU drives the coil pack slightly better than the old one. (I notice this ECU reports a higher battery voltage reading on the Lexia than the old ECU for the same voltage at the battery terminals too..perhaps unrelated but still interesting)

[stevieb]

[Thanks Steve,

I know that breather tube well - I've had it disconnected and pushed up out of the way a bit before, thankfully it hasn't broken on me! I will certainly treat it with care. Mind you my car is only coming up on 109k miles and I seem to recall you saying yours was approaching 200k ??! Twice the mileage would certainly make the plastics and rubber under the bonnet that much more brittle...

Ooh no, only 113k (was 112k) on mine at the mo. I've heard of these hoses going brittle at a lot less than 100k too, so maybe it depends on the precise grade of plastic used, or which day of the week they were fitted. Maybe whether the factory bod had had onions for lunch... Dunno. I work on the theory it's French, and the French have/had a reputation for going out on strike whenever they chose - and their products are often the same. Hard working when they work, but prone to downing tools and walking out if you say the wrong thing or the mood just takes them

So the engine drone increases when the engine is hot, but you've still not experienced any return of the invisible caravan ? It could be that your drone is your exhaust system, didn't you say you had a non-standard exhaust fitted ?

My original exhaust (whose rear silencer was all rust and no baffles) had a really loud drone/boom centred at 1500 rpm when I put my foot down but was relatively quiet higher up. The replacement exhaust system I fitted is quiet and boom free below 2000 rpm but now has a noticeable drone centred around 2500. Nothing too bad, but I do notice it on motorway cruising as its exactly the rpm I'm doing at 60-70mph. If I accelerate heavily at 2500 rpm it even sounds slightly raspy. I think its just the characteristic of the new exhaust system.

Yes and no. In recent times when the engine was working well (usually straight after a coilpack swap) the drone just never appeared and tickover was a wonderfully genteel affair. I have a stainless cat-back exhaust which I asked to be made as quiet as possible - I didn't want to sound like a yobbo. Unfortunately, whatever causes the drone (which has most often been the secondhand coilpack with the cracks in it) does make me sound like a yobbo with a louder and growlier exhaust note. I get numpties in VW Golf's trying to race me away from lights. When I had the invisible caravan, and again on the bad days this time around, they would've left me standing. Since the last few improvements (fuel pump connector, fuses, coil/connectors cleanup, injectors etc.) I'll leave them for dead - not that I make a habit of it I should add... It's very crude, but this tells me I'm on the right track, just not there yet because I haven't got the quietness back yet. Today's improvement gives me hope though

I'm off to the girlfriends in North Yorkshire later this evening, then spending the day with her tomorrow. My keys will be handed to her at some point for her appraisal. We live a good distance apart so she only gets to ride in the car intermittently - this means she's a far more honest judge of any changes, good or bad. Her past history as a rally navigator also means her ear is keener than most at hearing those changes

Nice. I think any good quality plug will see some improvement if the gaps on the old plugs were excessive. Did you compare the gaps of old and new ?

During cranking the spark is a lot weaker than idle due to lower battery voltage limiting the primary coil current, so the health of the ignition system including plugs has quite an effect on how quickly it "catches" when cranking.

In my case I noticed a difference in starting when swapping the ECU - my original ECU always took about half a second of cranking before it would fire, the one in the car now catches and fires instantly on the first revolution. My guess is that this ECU drives the coil pack slightly better than the old one.

I didn't bother with the feeler gauges, but there was a clear difference in the gap sizes between new and old. The new gap is 1.0mm, so I'd say the older one was knocking on 1.2-1.3mm. Quite a lot more. This comes back to my earlier comment about chasing problems - maybe my biggest problem was just plug erosion all along. There's no doubt the fuel pump connector was rotten and I had a duff injector, but if the sparks are weak then all those other minor niggles will be exaggerated. I've got a better, more reliable car at the end of the day, but if I'd changed the plugs first, maybe, just maybe...

[Mandrake]

Ooh no, only 113k (was 112k) on mine at the mo.

Somehow I thought you said it was approaching 200k...

Yes and no. In recent times when the engine was working well (usually straight after a coilpack swap) the drone just never appeared and tickover was a wonderfully genteel affair. I have a stainless cat-back exhaust which I asked to be made as quiet as possible - I didn't want to sound like a yobbo. Unfortunately, whatever causes the drone (which has most often been the secondhand coilpack with the cracks in it) does make me sound like a yobbo with a louder and growlier exhaust note. I get numpties in VW Golf's trying to race me away from lights. When I had the invisible caravan, and again on the bad days this time around, they would've left me standing. Since the last few improvements (fuel pump connector, fuses, coil/connectors cleanup, injectors etc.) I'll leave them for dead - not that I make a habit of it I should add... It's very crude, but this tells me I'm on the right track, just not there yet because I haven't got the quietness back yet. Today's improvement gives me hope though

Whatever problem still remains with mine seems to have a temperature relationship - it runs best cold, especially if I don't let it idle for too long before setting off, and gradually gets slightly worse after plenty of heat soak has occurred under the bonnet. The injectors are silent when cold but a couple get noisy when the engine is hot. Coincidence ? Maybe.

I think I've definitely nailed the ignition problems that were causing it to run poorly in wet weather for a long time last year - tonight was 5 degrees, wet and raining a fair amount, I started it up and drove off in under 30 seconds, it felt very eager, lots of power even at low rpm, went for about a 15 minute drive - absolutely perfect. It then sat stopped for 15 minutes then another 10 minute trip, again perfect. No loss of power at all despite the very wet conditions.

I can always tell its running well when its eager to accelerate at 1500 rpm in 2nd or 3rd with a light throttle. In fact 2nd gear pick up from low rpm is the most telling sign of good or bad performance.

When I refitted the new coil pack on Saturday I lightly greased inside the ends of the front spark plug boots and the top plug lead wire boots with Lithium grease before refitting - something that my Dad always used to advise on spark plug lead boots but which I hadn't tried on this car before, and I think it definitely does help in wet conditions.

I've previously tried silicon grease which is recommended for this purpose but next time I had the leads out I found the grease had solidified into lots of small dry lumps... something that the lithium grease doesn't do. (It becomes slightly fluid with heat but re-solidifies when it cools and doesn't dry out or go hard)

So this time I cleaned out the lumps of silicon grease and applied the lithium grease. I also noticed that the rubber boots on the new plug leads are quite a poor fit on the coil pack - I can wiggle the right hand one in particular and clearly see that there is a slight gap between the rubber of the plug lead boot and the coil pack plastic elbow. The rubber boot inside diameter is too big and doesn't fit snugly like it should. (could this be the cause of running well temporarily after swapping coil packs ? poorly fitting poorly sealing plug lead boots ?)

If there is a gap there there may be some corona discharge or electrostatic leakage through the gap in damp conditions...if the gap isn't too great the lithium grease forms an air tight seal that is also an insulator. (clean, dirt free plain lithium grease is a very good insulator and will keep moisture out too)

Dad used to use lithium grease under the anode cap on CRT TV's (which ran at 26,000 volts) to fix problems with EHT leakage, so if it works there it should work on ignition lead boots, as long as the grease can handle the temperature...should have listened to my Dad.

Next time I have the rear cassette out I'll grease inside each end of the plug boots on the rear bank as well.

I didn't bother with the feeler gauges, but there was a clear difference in the gap sizes between new and old. The new gap is 1.0mm, so I'd say the older one was knocking on 1.2-1.3mm. Quite a lot more. This comes back to my earlier comment about chasing problems - maybe my biggest problem was just plug erosion all along. There's no doubt the fuel pump connector was rotten and I had a duff injector, but if the sparks are weak then all those other minor niggles will be exaggerated. I've got a better, more reliable car at the end of the day, but if I'd changed the plugs first, maybe, just maybe...

I was going to say it looked about 1.3mm from looking at the picture - it would have been a good guess.

I think you'll find the plugs will improve the running significantly, but I strongly doubt that its the sole cause of your invisible caravan problems of last year, nor the very intermittent nature of the poor performance. The reason I say this is because I've had good spark plugs with the correct gap fitted for at least the last 6 months, and I was still having identical symptoms to you.

So I would say your worn plugs are a contributing factor and will help put the finishing polish on getting it run properly, but not the cause of the major problems that have had you running around cleaning ICV's etc... I still think that will turn out to be a sticky injector and/or a mixture imbalance between cylinders causing one or more lean running cylinders.

The lean running cylinder(s) then causes the fuelling and timing advance maps to get out of kilter which is temporarily improved by resetting the ECU...

[stevieb]

Speaking of resetting the ECU...

A quick report from a very soggy North Yorkshire. I decided to do an ECU reset this afternoon/evening before I headed up here to see how things changed. Apart from the early growliness and very high (950rpm) tickover on a completely cold start, the car has run like a dream. The drone is still there, but a lot less deafening, and power is increased enormously. I managed an average mpg of 31.7, which isn't bad considering I've always noticed a drop of a couple of mpg in heavy rain. On good days in the past a similar journey (in the dry) might get 33mpg. Bad days don't bear thinking about (21-22mpg )

My other very crude comparison method has seen me do around 125 miles of mixed driving (lots of standing in traffic this morning) on £20 of fuel. This is the minimum I'm aiming for, and is what I've managed today overall.

I think you're right about the mixture of issues, though I do wonder if I'd changed the plugs first whether the diagnoses elsewhere might've been a little easier. I reckon a weak spark will exaggerate so many other minor problems that could otherwise be ignored, that it really should've been top of my list - especially as swapping sparks was one of the earliest DIY jobs I did on this car to ensure it had good 'uns fitted...

That second gear test sounds familiar too - in my case I like to just see how quickly it picks up - usually upsetting those Golf boys at the same time

One thing you may not have even considered is that you've just about licked your problems - the injector issue is a minor one that can be fixed easily, and the heat issue might well be down to the incorrect oxygen sensor. I can't help but think you're nearly there

I don't know where the 200k came from, but I've read it somewhere recently too. Maybe a link somewhere...?

Lithium grease - is that the white stuff? Looks like Ian Holm's blood in the Alien film?

[Mandrake]

Speaking of resetting the ECU...

A quick report from a very soggy North Yorkshire. I decided to do an ECU reset this afternoon/evening before I headed up here to see how things changed. Apart from the early growliness and very high (950rpm) tickover on a completely cold start, the car has run like a dream. The drone is still there, but a lot less deafening, and power is increased enormously. I managed an average mpg of 31.7, which isn't bad considering I've always noticed a drop of a couple of mpg in heavy rain. On good days in the past a similar journey (in the dry) might get 33mpg. Bad days don't bear thinking about (21-22mpg )

950 rpm is pretty normal idle speed for a cold start within the first minute so I wouldn't worry about that. If it wasn't that high before on cold morning starts then maybe that might have been a problem.. If the performance is spot on I wouldn't worry too much about the drone from the exhaust - remember we're both expecting perfection out of 15 year old 110k engines! I would be happy if the performance was as it should be and wouldn't worry about a slight increase in noise.

Another thing to consider is that engine and exhaust noise increases dramatically with timing advance, but so does power. You may just find that the timing is now on average more advanced than it has been for a long time, giving the engine more of a rawty noise. I find my exhaust sounds more growly when its running well whereas when it wasn't running well the exhaust was quieter but a bit more boomy on wide throttle. Different kind of noise.

I think you're right about the mixture of issues, though I do wonder if I'd changed the plugs first whether the diagnoses elsewhere might've been a little easier. I reckon a weak spark will exaggerate so many other minor problems that could otherwise be ignored, that it really should've been top of my list - especially as swapping sparks was one of the earliest DIY jobs I did on this car to ensure it had good 'uns fitted...

I've been thinking about the relationship between mixture and ignition - a leaner mixture requires a higher spark voltage to ignite than a balanced mixture, (fuel is a conductor so causes the voltage across the gap to drop) so if a cylinder is running lean it will have more of a tendency to misfire with a weak spark than a cylinder running at the correct mixture.

So a (slightly) lean running cylinder with a good strong spark may not misfire, a slightly weak spark with a balanced mixture may not misfire, but a combination of a slightly lean mixture AND slightly weak spark could result in a misfire in that cylinder.

Fix either the mixture imbalance OR the weak spark and the misfire may go away even though you've only really fixed half of the problem.

Maybe we've come at the same problem from opposite directions - I fixed my ignition first (coils/leads/new plugs) and thus minimised any misfiring, but I still have a lean running cylinder somewhere due to a flow imbalance that occasionally misfires. (perhaps an intermittent imbalance due to a sticky injector)

You've (potentially) fixed a sticky or poorly balanced injector by swapping them, but you still have a weaker spark because the gap is (was) too wide on your plugs. With a better mixture balance between cylinders with injectors working properly a lean misfire is less likely even with a weaker spark. Fix the spark plugs as well and you may have solved the other half of the problem. (Assuming the leads are ok, which I wouldn't be certain of if they're originals)

That second gear test sounds familiar too - in my case I like to just see how quickly it picks up - usually upsetting those Golf boys at the same time

Foot flat to the floor is not what I mean by a pick up test. What I mean is 2nd/3rd gear at about 1500-2000 rpm up an incline, apply a small to moderate amount of throttle - if running well the torque is strong and instant, if running badly nothing happens! When I had that faulty coil pack in on Saturday there was absolutely NO acceleration or throttle response in those conditions even with 50-70% throttle. To accelerate I would have literally had to kick it down a gear.

One thing you may not have even considered is that you've just about licked your problems - the injector issue is a minor one that can be fixed easily, and the heat issue might well be down to the incorrect oxygen sensor. I can't help but think you're nearly there

Yeah its very close. When I say it's not running quite right sometimes we have to keep things in perspective - the "bad" days now are relatively small drops in power, its more the loss of throttle responsiveness that bothers me at lower rpm, a slight misfire or roughness that comes and goes at idle and the stumble if I flick the throttle. Even when those are present there is no major loss of power, it just doesn't feel as lively to drive. I feel these are all fuel related.

The symptoms have morphed a lot in the last year and a bit I've been trying to troubleshoot, I've also managed to introduce new problems along the way, such as replacing a slow/sluggish (carboned up) but otherwise working oxygen sensor with one that is the wrong spec for the car and doesn't warm up properly, replacing old spark plug leads with two intermittent breaks but damaging the new ones in the process - replacing old but "ok" NGK spark plugs with new Bosch ones of the wrong type and heat range which then started fouling up badly and misfiring with short runs etc... For a while I was making one step forward and two steps back.

I clearly remember that before I changed the oxygen sensor, and while I still had very noisy tappets (as noisy or worse than those in your videos) that if I started the car and drove off quickly afterwards the low rpm performance would usually sag within a couple of minutes, especially if the engine was revved. But if I let the car idle for say 5 minutes before driving off, performance was much better and more consistent.

At the time I put this down to very noisy tappets when cold triggering the knock sensor - drive off quickly and rev the engine while the tappets are clattering away and there was so much mechanical noise that the knock sensor dialled back the timing and killed the performance. Once this happened the timing would tend to stay retarded for some time. (Possibly it was shifting to a low octane map which would keep it retarded for hours/days of driving)

However idle for a few minutes, let oil circulate and warm up and the tappet noise would drop quite a bit, then drive off and there wasn't enough noise to trigger the knock sensor. So it seemed anyway.

Later on I used an additive and a bit later a couple of oil changes and the tappets are now silent when cold, however meanwhile I replaced the oxygen sensor with one whose heater doesn't warm up properly - so the symptoms have reversed! If I start the car and let it idle for 5-10 minutes before driving off the car runs worse, and I believe its because the partially warmed up oxygen sensor (which is not warming up fully until actually driving) causes the ECU to adjust the fuel trim too rich. (A partially warmed up oxygen sensor biases towards a "too lean" signal)

If I start the car and drive off straight away the oxygen sensor warms up quickly from exhaust heat and passes through the "danger zone" of being partially warmed up in seconds. Meanwhile the tappets are nice and quiet when cold so driving away cold doesn't cause any performance problems.

Sounds crazy doesn't it ? The symptoms of whether its better to idle before driving off or not have definitely swapped around. I'm sure that once I get this oxygen sensor replaced for the correct one idling for a long time before driving won't cause performance issues any more.

Lithium grease - is that the white stuff? Looks like Ian Holm's blood in the Alien film?

No not the white stuff - white lithium grease has PTFE added to it. (silicon grease is white too, in case you're thinking of that)

Normal multi-purpose lithium grease is a kind of yellowy brown colour, thin and slightly transparent. Like this:



It has no conductive additives in it like copper slip and some other automotive greases.

[stevieb]

Interesting reading Simon - now let's see if my (unintentional) experiment today throws any more light on matters.

Before I start, keep in mind that yesterday I managed 120-odd miles on £20 of fuel, yet the 120-130-odd miles I've done since then (13 last night from petrol station to here, then a round-trip to Shildon and back this afternoon) has got through virtually £30 of fuel - and almost all on the way back from Shildon.

Away from the garage last night I was careful not to let the ignition sit in position II for too long before starting - like before, firing up the engine before the warning lights go out. The outbound journey earlier was the same. On both journeys the car was healthy sounding, ran well, and mpg was good (70ish mph on the A1 was getting 30-45mpg depending on gradient). However, without thinking, I started the engine before heading back AFTER the ignition had been in position II for about 15 minutes (the engine was still warm at this point, but not so much it was showing on the temp gauge). Power-loss wasn't too bad, but the drone was deafening again and fuel consumption was horrendous. My girlfriend even commented when we got to the country roads that "she sounds very noisy again". I pulled into a lay-bay, knocked-off the ignition, took the key out and then re-started quickly. Suddenly we're back to quiet, smooth and economical mode despite a warm start.

Something is definitely happening when the key is in position II for too long. Whether it's like I said before and the ECU is having the time to re-load incorrect parameters - I've said before that I think the ECU only applies new parameters at start-up, not mid-journey, so maybe it's adjusting for the weak spark/bad ignition it detected at the oxygen sensor on the previous journey (as yours may do with the incorrect sensor) and applying those settings. Firing-up immediately might by-pass these settings and so the ECU either works with preset defaults or simply does things on-the-fly.

OR something is happening with the fuel pressure during this time - I say this because my drone was a permanent feature before I cleaned up the fuel pump terminals. This would suggest either the pump is nodding off to sleep, pressure is leaking off somewhere (my fuel drop when it's like this resembles a leak), or there's a vacuum issue at startup which is affecting the pressure regulator and continues to affect the pressure during the journey (maybe some vapour-lock somewhere). The only argument against this problem being caused by a drop in fuel pressure is that the power delivery doesn't drop too much (when I had dirty fuel pump terminals my power was very low). Maybe having the drone with low fuel pressure was a sign of that AND bad sparks.

I need to sort my other three sparks and see what changes, don't I?

Right, I'll reply to your post in a mo Simon

[stevieb]

Foot flat to the floor is not what I mean by a pick up test. What I mean is 2nd/3rd gear at about 1500-2000 rpm up an incline, apply a small to moderate amount of throttle - if running well the torque is strong and instant, if running badly nothing happens! When I had that faulty coil pack in on Saturday there was absolutely NO acceleration or throttle response in those conditions even with 50-70% throttle. To accelerate I would have literally had to kick it down a gear.

Hehehe, the best bit is the lack of foot to the floor - when things are going well it just wafts up to silly-mph without any real effort. I agree on the other bits too - the revs rise a lot easier, almost like slack has been taken out of the throttle cable. On a bad day it feels like the cable is sloppy and loose.

Yeah its very close. When I say it's not running quite right sometimes we have to keep things in perspective - the "bad" days now are relatively small drops in power, its more the loss of throttle responsiveness that bothers me at lower rpm, a slight misfire or roughness that comes and goes at idle and the stumble if I flick the throttle. Even when those are present there is no major loss of power, it just doesn't feel as lively to drive. I feel these are all fuel related.

The symptoms have morphed a lot in the last year and a bit I've been trying to troubleshoot, I've also managed to introduce new problems along the way, such as replacing a slow/sluggish (carboned up) but otherwise working oxygen sensor with one that is the wrong spec for the car and doesn't warm up properly, replacing old spark plug leads with two intermittent breaks but damaging the new ones in the process - replacing old but "ok" NGK spark plugs with new Bosch ones of the wrong type and heat range which then started fouling up badly and misfiring with short runs etc... For a while I was making one step forward and two steps back.

I clearly remember that before I changed the oxygen sensor, and while I still had very noisy tappets (as noisy or worse than those in your videos) that if I started the car and drove off quickly afterwards the low rpm performance would usually sag within a couple of minutes, especially if the engine was revved. But if I let the car idle for say 5 minutes before driving off, performance was much better and more consistent.

At the time I put this down to very noisy tappets when cold triggering the knock sensor - drive off quickly and rev the engine while the tappets are clattering away and there was so much mechanical noise that the knock sensor dialled back the timing and killed the performance. Once this happened the timing would tend to stay retarded for some time. (Possibly it was shifting to a low octane map which would keep it retarded for hours/days of driving)

However idle for a few minutes, let oil circulate and warm up and the tappet noise would drop quite a bit, then drive off and there wasn't enough noise to trigger the knock sensor. So it seemed anyway.

Later on I used an additive and a bit later a couple of oil changes and the tappets are now silent when cold, however meanwhile I replaced the oxygen sensor with one whose heater doesn't warm up properly - so the symptoms have reversed! If I start the car and let it idle for 5-10 minutes before driving off the car runs worse, and I believe its because the partially warmed up oxygen sensor (which is not warming up fully until actually driving) causes the ECU to adjust the fuel trim too rich. (A partially warmed up oxygen sensor biases towards a "too lean" signal)

If I start the car and drive off straight away the oxygen sensor warms up quickly from exhaust heat and passes through the "danger zone" of being partially warmed up in seconds. Meanwhile the tappets are nice and quiet when cold so driving away cold doesn't cause any performance problems.

Sounds crazy doesn't it ? The symptoms of whether its better to idle before driving off or not have definitely swapped around. I'm sure that once I get this oxygen sensor replaced for the correct one idling for a long time before driving won't cause performance issues any more.

Crazy? Definitely Like I say, I wonder whether if you or I had taken one single different course of action in our quest for a solution, we might well have "cured" the worse bit of the problem and merrily gone on our way for a while, and then when it cropped up again we would've correctly looked into other possible causes. I know it's mostly down to luck, rather than judgement, but I still wonder if I missed an obvious tell somewhere along the way. A good example is the suspension noise I had last summer - it's just beginning to return now, but can I remember what it was I changed that fixed it last time...?

Bah, hindsight is a wonderful thing ain't it...?

Normal multi-purpose lithium grease is a kind of yellowy brown colour, thin and slightly transparent. Like this:



It has no conductive additives in it like copper slip and some other automotive greases.

It may have been silicone grease I was thinking of - the stuff that's often used to lubricate small plastic gears in novelty items (those novelty items my sister buys then hands to me to fix when they break ).

[myglaren]

I had a tin of Castrol Lithium HMP grease for years, got sick of seeing it and chucked it in the end.
It was whiter and more opalescent than that Simon has posted but not much.

Perhaps you are thinking of white grease ? That gets used quite a bit on plastic parts.

[lexi]

Lithium grease is generally the colour of Simons pic. It is soap based and eats rubber. It will lighten when very old as it degrades.
It is generally used in ball joints.

[Mandrake]

Lithium grease is generally the colour of Simons pic. It is soap based and eats rubber. It will lighten when very old as it degrades.
It is generally used in ball joints.

While its true that lithium grease is not good for natural rubber, (over a long period of time) neither is engine oil, LHM, petrol or diesel. It's basically just a light grade of refined oil with a lithium based soap added as a thickener to make it into a grease, so its chemical properties are similar to light oil.

I might be wrong, but I very much doubt that spark plug lead boots made in the last 30 (maybe even 40) years are natural rubber, they'll be some grade of oil resistant synthetic rubber such as nitrile, if so they will not be harmed by lithium grease and certainly not from a thin smear on the inside of the boot. I've used it on cars as old as the GS and never noticed any problems with plug lead rubber damage years later.

Anything that is safe with engine oil or LHM is safe with lithium grease - for example I use it on the seals in the hydraulic system on an LHM car such as fitting new seals in the hydraulic pump. (If you don't use some sort of grease when re-fitting the o-rings have a high chance of being pinched and damaged) It's probably ok on an LDS system as well, and definitely ok on any seals that seal engine / gearbox oil. Also anything that can withstand petrol or diesel will not be harmed by it.

One area I wouldn't use it though is on the seals in a DOT 4 brake system, which are not compatible with mineral oils therefore won't be compatible with mineral lithium grease.

It's a good general purpose grease that is generally safe to use on most things but not natural rubbers. (Even then deterioration is very slow) Temperature rating is typically about 135 degrees C so can be used on the exterior of an engine (for example on the plug lead boots) without worrying about it melting and running away, although it will soften slightly above 100 degrees and re-set when cooled. (It's also somewhat sticky so tends to stay put even when softened)