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

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

Post by larppaxyz »

Mandrake wrote:
larppaxyz wrote:It's been around three or four weeks since i did that and it's been much better. Not perfect still, but there is no 3500rpm lag appearing yet.

Right now my car is waiting for new belt(s), tensioners, water pump and most importantly new engine mount rubbers. Cost ~1000 euros inc. labour.
How's your car running lately ? If you're still having problems with low rpm performance and pickup could you try blanking off the right hand lower spigot on the throttle butterfly as described above ? I'd be interested to see what difference if any you notice.
It's back to old behaviour, belt and tensioners made no difference. If anything, could be worse.

I will try what you suggest as i don't really have any other ideas left.

As a side note, there is one thread on 406 coupe club forum with same issues and after replacing some sensors and trying all sorts of other things this guy finally replaced ICV and that fixed it. ICV appeared to be working and he even cleaned it, but problem was that it would still not hold it's position while driving and that caused symptoms that are pretty much what i have been experiencing. http://www.406coupeclub.org/PHPBB3/view ... 83&t=43996" onclick="window.open(this.href);return false; is the link, but you need to register first. Check these two also (ICV teardown and ICV calibration) http://www.406coupeclub.org/PHPBB3/view ... 83&t=44302" onclick="window.open(this.href);return false; and http://www.406coupeclub.org/PHPBB3/view ... 83&t=44110" onclick="window.open(this.href);return false;

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

Post by Mandrake »

larppaxyz wrote:
Mandrake wrote:
larppaxyz wrote:It's been around three or four weeks since i did that and it's been much better. Not perfect still, but there is no 3500rpm lag appearing yet.

Right now my car is waiting for new belt(s), tensioners, water pump and most importantly new engine mount rubbers. Cost ~1000 euros inc. labour.
How's your car running lately ? If you're still having problems with low rpm performance and pickup could you try blanking off the right hand lower spigot on the throttle butterfly as described above ? I'd be interested to see what difference if any you notice.
It's back to old behaviour, belt and tensioners made no difference. If anything, could be worse.

I will try what you suggest as i don't really have any other ideas left.
Easy to try, and it seems to have made a major difference on mine, although it has only been 3 days.
As a side note, there is one thread on 406 coupe club forum with same issues and after replacing some sensors and trying all sorts of other things this guy finally replaced ICV and that fixed it. ICV appeared to be working and he even cleaned it, but problem was that it would still not hold it's position while driving and that caused symptoms that are pretty much what i have been experiencing. http://www.406coupeclub.org/PHPBB3/view ... 83&t=43996" onclick="window.open(this.href);return false; is the link, but you need to register first. Check these two also (ICV teardown and ICV calibration) http://www.406coupeclub.org/PHPBB3/view ... 83&t=44302" onclick="window.open(this.href);return false; and http://www.406coupeclub.org/PHPBB3/view ... 83&t=44110" onclick="window.open(this.href);return false;
Ahhh, thank you very much for finding that! =D>

I've registered on that forum to read the threads and will post to that main thread some time soon to contribute my experiences with this problem because it does sound like the exact same symptoms I've seen.

As it happens I think my ICV is in need of cleaning - I often have the symptoms of "near stall" when coming to a stop where the revs dip down to about 500rpm then recover. I suspect the ICV is sticky and is not able to make small precise movements but instead sticks in place until commanded to make a large movement at which time it lurches slightly, thus idle speed is not regulated accurately.

From what I've read in those threads it looks like this is a common problem with the ICV and may in fact be related to the performance problems we're seeing.

With what I've discovered with the charcoal canister purge line and what I've read in those threads you linked I now believe that the root cause of our problem is poor mixture regulation under varying load conditions due to poor regulation and control of the air flow into the manifold, leading to the engine alternately running too lean or too rich. When it runs too lean it may misfire or knock, with knock leading to retarded timing.

As well as the butterfly vane there are three sources of air flow into the manifold:

1) The sump breather pipe on the bottom left of the butterfly assembly - in theory there shouldn't be any significant flow here, but if one of the o-rings on the pipe was leaking it could potentially introduce a random vacuum leak. I don't think this is the problem in my case though.

2) The charcoal canister purge valve - the hose on the bottom right I've blocked off at the moment. This valve opens progressively when accelerating and if there is a vacuum leak on the other side of the electrovalve it will lean the mixture out inappropriately.

3) The ICV valve - although primarily there to control the idle speed, if this valve doesn't stay accurately at the same opening when the engine is revved under load the mixture will wander due to variations in the air bypass. For example if the valve physically swings open during acceleration it may lean the mixture out the same as number 2 above.

One further possibility is that the ECU is designed to compensate for the vacuum loss caused by the canister purge valve opening by slightly closing the ICV and then opening the ICV again when the canister purge valve is closed. In that case a sticky ICV that cannot make a small accurate adjustment to the air bypass will not compensate for the vacuum change introduced by the canister purge valve.

Perhaps what is happening is that my ICV is sticky so the ECU can't use it to compensate for the purge valve, by blocking off the purge valve I remove the source of varying vacuum leak so that the ICV doesn't have to compensate for it - and the mixture is much more stable so the engine runs better, yet the sticky ICV is the real source of trouble. Interesting thought! :shock:

By the way have you tried the ICV "calibration" process described in that thread ? Ignition on (but not started) for 10 seconds, then off for 10 seconds, then repeat twice more ? I've never heard of this process before but I have almost certainly done it by accident many times when running Lexia sessions! Perhaps that could also explain some of the randomness of the symptoms I've seen.

I'm going to try this calibration process tomorrow.

addo
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Post by addo »

As I suggested, the timing belt change makes nil difference in a correctly timed motor.

The idle controller is a very simple device; all you are doing with a reset is setting the stops. If the ECU says more air, it will open further. I think you'd find it can also work like an anti-stall dashpot on a late carbed car, "kicking" the fuel/air feed slightly if the idle is dropping too low.

If you take it off and toggle it with brief pulses of battery voltage, you can also see how readily it slips back and forth (ie; if it's sticky). It would also be surprising if it doesn't self-calibrate in service.

It's really at a point where you might compare all injector signals at the plug with test lights, and also test up the coils/leads with a flying earth as I did on the job recently - this way you can see the pairs of plugs and A:B their spark intensity. If all is good on a hot motor, then you're at the point of ECU substitution.

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Mandrake
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Re:

Post by Mandrake »

addo wrote:As I suggested, the timing belt change makes nil difference in a correctly timed motor.
I didn't think it would make any difference either, so I'm not surprised. Not that it's a bad thing having the timing belt done! I'm certainly running a risk on mine...
The idle controller is a very simple device; all you are doing with a reset is setting the stops. If the ECU says more air, it will open further. I think you'd find it can also work like an anti-stall dashpot on a late carbed car, "kicking" the fuel/air feed slightly if the idle is dropping too low.
Well the ECU controls the idle through the ICV via a feedback loop - if the rpm is below idle speed it simply increases the opening percentage until its back at the correct speed. If the ICV is working smoothly the change will be subtle and smooth. If it sticks and can only move in lurches then when a load comes on (A/C, radiator fans etc) the extra delay will cause the rpm to droop a lot lower than it should, then when the ICV finally does move it will over compensate and the revs will overshoot the desired target.

This is exactly what mine does - when a load change occurs the revs dip down to near stalling then surge above the correct revs and then drop back to normal again. It does this when the A/C kicks in, radiator fans kick in in particular, but it also does it when I pull to a stop and the gearbox changes from 2nd to 1st just as you're stopping.
If you take it off and toggle it with brief pulses of battery voltage, you can also see how readily it slips back and forth (ie; if it's sticky).
That's exactly what I was thinking of trying when I take the valve off, if you read one of the linked threads you'll see pictures of the inside of a faulty valve that have been cut open - some get sticky due to carbon/muck build up and can be cleaned, however when they get really bad it seems to be that the bearing at one end develops a lot of play, the play introduces enough slop that the rotating section of the valve intermittently drags on the housing. There is a picture of one where the rotating section is obviously scuffed, and that was out of a 70k mile car.

So just because it turns to the limit stops with a full 12 volts applied doesn't necessarily mean it is turning smoothly for small corrections, and I think the key to the problem - both the dipping idle and poor idle regulation, and the poor mixture regulation while driving is that the valve is not able to make small precise adjustments and stay where the ECU wants it.

Sadly at around £200 new a new one is out of the question! So cleaning it or obtaining a second hand one would be the only way of dealing with it if it is the cause.
It would also be surprising if it doesn't self-calibrate in service.
I can't quite see myself what the "calibration" would be doing either... especially if that calibration process occurs with the engine not running. But I'll try it anyway.
It's really at a point where you might compare all injector signals at the plug with test lights, and also test up the coils/leads with a flying earth as I did on the job recently - this way you can see the pairs of plugs and A:B their spark intensity. If all is good on a hot motor, then you're at the point of ECU substitution.
I can't agree really, I thought I was at the point of ECU substitution a week ago but now that I've discovered the effects of blocking off the purge solenoid and read this guys thread I'm following a different line of thinking entirely.

Read his "invisible caravan" thread (don't worry, its only a few pages, not 60+ pages :lol: ) and its almost like reading a version of my thread from an alternative universe. He's had the exact same symptoms as me and larppaxyz, has tried many of the same things as me and developed some identical theories, he's thought 100% that he's fixed the problem on several occasions only to have the problem come back days or weeks later, the difference is he seems to have finally nailed it once and for all... :)

I believe that I've had additional unrelated problems thrown into the mix too - fouled spark plugs at one point (and possibly again now) failed coil pack and leads etc, but even with those issues sorted out the underlying intermittent performance problem remained, particularly at low rpm. A mixture control problem is most likely what is causing my spark plugs to foul as well, so I think if I fix this problem I'll have no more spark plug fouling.

And finally, thinking back last year, the performance did start to go down hill at around the same time that the idle speed started surging - sometimes it was bad enough that after a hot start the engine would nearly stall, surge above idle, nearly stall etc as much as three times in a row before finally settling down. There was no idle speed surging problem back when the engine performance was 100% in the first 6 months that I had the car...

I've been suspicious of the ICV for a long time now, but only in relation to the idle control/surging issues, what's new is the realisation that it may be screwing with the mixture while driving and causing performance issues as well.

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

Post by larppaxyz »

I think we could be on to something now. What i'm going to try before i do anything else, i take my ICV apart to clean and lube it, giving it some special quality time on my workbench. I hope to do this in few days.
Mandrake wrote: By the way have you tried the ICV "calibration" process described in that thread ? Ignition on (but not started) for 10 seconds, then off for 10 seconds, then repeat twice more ? I've never heard of this process before but I have almost certainly done it by accident many times when running Lexia sessions! Perhaps that could also explain some of the randomness of the symptoms I've seen.

I'm going to try this calibration process tomorrow.
I haven't tried this calibration yet, i have never heard of it before, but hey who knows? :)

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

Post by Mandrake »

larppaxyz wrote:I think we could be on to something now. What i'm going to try before i do anything else, i take my ICV apart to clean and lube it, giving it some special quality time on my workbench. I hope to do this in few days.
I'm tempted to take mine off today and give it a clean with carb cleaner, I wonder if the rotating section is gummed up with oil and varnish deposits, as my air intake system in general is very oily. Be careful stripping it down though, it looks like you can easily get into trouble with getting it back together, and a new one is £200! I'm going to try to clean it through its ports and by applying a small amount of power to turn it as I clean it, but I'm not brave enough to attempt a strip down.
Mandrake wrote: By the way have you tried the ICV "calibration" process described in that thread ? Ignition on (but not started) for 10 seconds, then off for 10 seconds, then repeat twice more ? I've never heard of this process before but I have almost certainly done it by accident many times when running Lexia sessions! Perhaps that could also explain some of the randomness of the symptoms I've seen.

I'm going to try this calibration process tomorrow.
I haven't tried this calibration yet, i have never heard of it before, but hey who knows? :)
Well I just tried this "calibration" procedure not really expecting anything to happen but something seems to have changed... it has already been running a lot better the last 3 days since I blocked off the canister purge line but it seems even better again now.

What's really noticeable is that even right from cold the engine has oodles of effortless torque as low as 1500rpm and pulls away at low revs smoothly and responsively without requiring much throttle at all. :) What the calibration has done I have no idea, and it asks more questions than it answers:

1) Will the effect only be temporary, like resetting the ECU ?
2) Does resetting the ECU also reset this calibration, and if not does it need to be re-done after the battery is disconnected ?

The idle speed is still surging however. I do feel like we could be finally homing in on the truth. :)

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

Post by Mandrake »

Well I was going to try to remove the ICV by itself today for cleaning and inspection however whilst it might be possible on a 406 it doesn't seem to be possible to get enough access on a Xantia without removing the inlet manifold thanks to the close proximity of both the LHM tank and the coolant expansion chamber #-o The two Allen bolts holding the valve can be reached but not the hose clamps attaching the underneath of the ICV to the throttle body, which on mine are still the original awkward to remove crimp types as well. (Which I will change to jubilee types)

I was planning to take the manifold out tomorrow to swap the spark plugs and manifold gasket anyway so I can do it then, however I then won't know for sure if there is an improvement whether its the ICV or the other things I'm disturbing...

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

Post by larppaxyz »

Mandrake wrote:Well I was going to try to remove the ICV by itself today ...
I actually removed it today after all. It's 5 min job on 406. I took it inside an took a good look into air channels without taking it apart and i noticed that it's very filty. I have small fingers so i tried to rotate flap and i felt it was very stiff. So i really flooded it with CRC while rotating flap with my finger and shaking it around. Black goo was dripping from it and i sprayed some more CRC into it. After repeating this few times, flap started to move almost freely and now when i shake it, i can here flap clunking away. Before it didn't make any noises when shaking it on my hand.

After refitting it, without resetting ECU and without doing ICV calibration first thing i noticed that idle rpm is somewhat lower than it was before, around 50-100 rpms lower and not wandering at all. So i took it to a test drive and oh boy.. throttle response is much smoother, it doesn't try to stall when stopping to red light, i actually shows 0l/100km when taking your foot of the throttle while engine braking. After driving around for 20 minutes fast and slow, 3500 rpm spike was gone and i felt like it had much more torque on lower rpm area. As as big bonus i noticed that gearbox started to learn new tricks and gear changes came smoother and smoother while driving. I had some trouble when slowing down and changing from 2nd to 1st, this is now much smoother.

All in all, we have seen before that tomorrow it can be back to old habits, but ... for now, it feels like a fixed problem. And i really hope it stays that way this time.

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

Post by Mandrake »

larppaxyz wrote:
Mandrake wrote:Well I was going to try to remove the ICV by itself today ...
I actually removed it today after all. It's 5 min job on 406. I took it inside an took a good look into air channels without taking it apart and i noticed that it's very filty. I have small fingers so i tried to rotate flap and i felt it was very stiff. So i really flooded it with CRC while rotating flap with my finger and shaking it around. Black goo was dripping from it and i sprayed some more CRC into it. After repeating this few times, flap started to move almost freely and now when i shake it, i can here flap clunking away. Before it didn't make any noises when shaking it on my hand.

After refitting it, without resetting ECU and without doing ICV calibration first thing i noticed that idle rpm is somewhat lower than it was before, around 50-100 rpms lower and not wandering at all. So i took it to a test drive and oh boy.. throttle response is much smoother, it doesn't try to stall when stopping to red light, i actually shows 0l/100km when taking your foot of the throttle while engine braking. After driving around for 20 minutes fast and slow, 3500 rpm spike was gone and i felt like it had much more torque on lower rpm area. As as big bonus i noticed that gearbox started to learn new tricks and gear changes came smoother and smoother while driving. I had some trouble when slowing down and changing from 2nd to 1st, this is now much smoother.

All in all, we have seen before that tomorrow it can be back to old habits, but ... for now, it feels like a fixed problem. And i really hope it stays that way this time.
Fantastic, that's very encouraging news. :)

I'll definitely be thoroughly cleaning my ICV when its out, I have a spray can of carb/intake cleaner that will hopefully do the job.

If your idle speed was too high before (640rpm is normal when hot with no accessory load) that suggests that not only was it stiff but that the ECU was actually unable to rotate it sufficiently far in the closed direction to get the idle down to the correct speed.

Glad to hear that it doesn't try to stall when stopping at the lights now - mine is still doing that even with the spigot blocked off, and a stiff/sticking ICV fits the symptoms perfectly.

The spike in power at 3500 rpm I believe is actually a sudden drop in power below 3500 rpm due to memorised knock retard caused by the engine knocking on an over lean mixture - in turn apparently caused by the ICV not closing properly.

After a period of time running in an intermittently lean under load condition with the engine knocking the knock retard table gets filled with large amounts of retard and low rpm performance suffers badly. Above 3500 rpm I believe the ECU is less sensitive to knock (higher knock threshold) and is therefore less prone to apply knock retard thus the sudden step in performance above 3500 rpm as less (or maybe no) knock retard is getting applied above 3500 rpm.

Now you've fixed the problem with the ICV and mixture regulation is working properly again the engine stops knocking under load and after 20 minutes of driving under varying loads the ECU learns the new conditions and the knock retard table is gradually reverted back to normal, minimal levels of knock retard. (Or none at all if you're on 98 fuel) An ECU reset would have done this immediately.

I'm not surprised that the gearbox is changing more smoothly either - I've noticed the exact same thing with mine, when the engine is low on power and misfiring the gear changes start to become very erratic and either "snatch" abruptly or (the opposite problem) the rpm "flares" up when shifting. When the engine is performing smoothly the gear changes become much better and more consistent.

I believe the reason for this is that the gearbox relies heavily on an engine torque figure which is calculated by the engine ECU and sent to the gearbox ECU. (this figure can be monitored in parameters measurement in the gearbox ECU, measured in Nm) This torque figure is used by the gearbox to predict how much clutch pressure is required, how quickly to ramp clutch pressures up and down, and how much clutch overlap is required to produce a smooth shift.

If the engine ECU over estimates the developed torque (as it does when it's misfiring) then the gearbox will not shift gears smoothly. It will try to adapt to the error in the torque figure but if the error is constantly changing due to an intermittent misfire that comes and goes then it will never adapt properly, so you end up with gear change quality constantly changing but never being good or consistent.

As soon as you solve the mixture regulation problem the ECU will start reporting the correct torque and the auto adaption of the gearbox ECU will settle down and adapt correctly, although an auto adaptive reset would speed up this process as well.

As you say its early days yet, so please let me know whether the problem comes back or whether it continues to run well. :) [-o<

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

Post by larppaxyz »

Mandrake wrote: Fantastic, that's very encouraging news. :)

I'll definitely be thoroughly cleaning my ICV when its out, I have a spray can of carb/intake cleaner that will hopefully do the job.
After that you should spray some lubricant there too, i think i managed to get some of my CRC to flap bearings... not sure if it's good because CRC usually leaves parts bone dry.
Mandrake wrote: Glad to hear that it doesn't try to stall when stopping at the lights now - mine is still doing that even with the spigot blocked off, and a stiff/sticking ICV fits the symptoms perfectly.
Yeah, sometimes it stalled when driving slowly and shifting from 1st to 2nd. And with hot engine it wasn't too uncommon for it to almost stall when stopping (that sweet 500rpm drop).
Mandrake wrote: The spike in power at 3500 rpm I believe is actually a sudden drop in power below 3500 rpm due to memorised knock retard caused by the engine knocking on an over lean mixture - in turn apparently caused by the ICV not closing properly.

After a period of time running in an intermittently lean under load condition with the engine knocking the knock retard table gets filled with large amounts of retard and low rpm performance suffers badly. Above 3500 rpm I believe the ECU is less sensitive to knock (higher knock threshold) and is therefore less prone to apply knock retard thus the sudden step in performance above 3500 rpm as less (or maybe no) knock retard is getting applied above 3500 rpm.
Yeah, power range over 3500rpm has been pretty constant all this time, i think ECU uses precalculated values for most of the calculations when WOT and >3500rpm.
Mandrake wrote: Now you've fixed the problem with the ICV and mixture regulation is working properly again the engine stops knocking under load and after 20 minutes of driving under varying loads the ECU learns the new conditions and the knock retard table is gradually reverted back to normal, minimal levels of knock retard. (Or none at all if you're on 98 fuel) An ECU reset would have done this immediately.
Yes, i didn't reset my ECU because i didn't wan't anything to mislead me with this ICV fix. I quess i could do it later to make sure everything is cleared.
Mandrake wrote: As you say its early days yet, so please let me know whether the problem comes back or whether it continues to run well. :) [-o<
I will keep you informed :) [-o< [-o<

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

Post by Mandrake »

larppaxyz wrote: After that you should spray some lubricant there too, i think i managed to get some of my CRC to flap bearings... not sure if it's good because CRC usually leaves parts bone dry.
I have just the stuff for that - LPS 1 is a penetrating lubricant which does leave behind a thin dry lubricating film in the bearing (if I can get it into the bearings) that is also corrosion resistant and is a dust and water repellent.

I'll use the carb cleaner first to dissolve and flush out the gunk which is probably carbon and oil fume buildup as you find in a dirty throttle butterfly, and then follow it up with a flush of LPS as well to try to soak the bearings. Any excess will drain out but a lubricating film will be left on the moving surfaces.
Yeah, sometimes it stalled when driving slowly and shifting from 1st to 2nd. And with hot engine it wasn't too uncommon for it to almost stall when stopping (that sweet 500rpm drop).
Mine never tried to stall going from 1st to 2nd, but it is common for it to dip to 500 rpm and stumble then recover when slowing to a stop, (in fact it does it nearly every time nowadays) also it sometimes stumbles and recovers multiple times in a row after a hot start, occasionally on a hot start it will even stall and not recover at all then be fine after restarting it.
Yeah, power range over 3500rpm has been pretty constant all this time, i think ECU uses precalculated values for most of the calculations when WOT and >3500rpm.
I've read that some ECU's ignore the knock sensor entirely above a certain cut-off rpm as the engine becomes too noisy to reliably "hear" knock at these higher speeds in amongst mechanical noise. I don't know for certain if the MP7.0 is one such ECU but given the massive abrupt change in performance at a threshold rpm when symptomatic it seems very likely.

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

Post by lexi »

So after 82 pages we have a valve that needs a squoosh of wd 40 in it? Thankfully it was nothing complicated!! :-D

That reminds me.........I need to lube one of my hinges. I don't want forces and friction of an untoward nature causing eerie noises which may set off my knock sensors thereby confusing my ECU'S into thinking I have a caravan :shock: :lol:

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

Post by Mandrake »

The fat lady hasn't sung yet Alex, but hopefully she's back stage warming up. :twisted:

When its run perfectly for several weeks in a row, then I'll celebrate...

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

Post by larppaxyz »

It still doesn't work.

Today, wen't to office, no problems, very nice and smooth. After leaving there afternoon, starting my car and i noticed that it doesn't idle smoothly anymore. On a 10km trip it stalled about 5 times, once shutting down engine completely (i was idling, waiting for red light).

Actually, since belt replacement, this has gone from bad to worse. Now that i run 60mph on a steady throttle on highway, it soon starts to sputter real badly, stalling for 0.5 - 2 seconds completely. If put it to neutral (while still having around 60mph speed) engine easily dies and i have to restart it. I have some history with this and it has been related to engine temperature and fans or thermostat kicking in. I have been suspecting that it's because stupid placement of engine temperature sensor (for ECU)(already replaced) and bleeding my cooling system have helped, this generally haven't been issue for me on these three years i have owned my car but now it is. When they replaced my belt and i picked up my car, there was way too little water on cooling system and i topped it up. So there is slim change that there could be air in the system but i've been trying to bleed it twice today without any affect to engine stalling.

I really gave it a beating today, italian tuneup for sure, and it looks like 3500rpm spike didn't creep back and power is there, but otherwise it's back to crappy idle again.

So is my ICV simply stuck again, or is this something else? Maybe is should just burn this piece of *hit.

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

Post by larppaxyz »

After my last message i went to look my ICV once more. I took it out and it was just like it was day before, not stuck at all.

So... after putting it back to car, engine was idling and went for a ride to pick up my diagnostic laptop so i could reset my ECU and see if it makes any difference. While driving car was stalling and sputtering so badly, i was afraid that it could actually cause damage to engine. At this point i didn't really care.

I got my diagnostic laptop and after some issues with laptop i finally got to read error codes from ECU. I was expecting to see 'speed sensor failure' that is very common and not real failure but caused by diagnostics itself. But there was a error code like "intake manifold pressure sensor failure - short or loose connector" (something like that). What the hell? I have replaced it once already, can't be that. Took a ride after ECU reset and error code clearing and sputtering and stalling continued. I went to a parking lot and while engine was idling i touched the sensor and engine cut out. I restarted and did that few times with same results. Wow! I have problems with intake manifold pressure sensor, i moved around the wiring and luckily i had original sensor in my glowbox and i installed it right away and headed back to home. All sputtering and stalling was now gone!

So what happened here? They must have damaged the sensor wiring when they replaced my belt, it's located such way that connector must be removed to get clear access to belt and tensioner parts. So what they actually did in service costing me 920 euros :

- Changed belt and tensioner
- First ordered wrong water pump
- Didn't found parts to replace engine mounts (they are not made anymore, they said)
- Left power steering fluid below MIN level, causing stuttering on steering wheel (i topped it up myself)
- Didn't top up cooling system, causing coolant level warning to lit
- Damaged intake manifold pressure sensor or sensor wiring causing my car to be almost undrivable.

Se we are back to chapter 1, original, long standing issue was ICV. This stuttering and sputtering (is there any better way to say it?) was caused by belt replacement and really added some confusion to this problem.

So ... [-o< [-o< [-o< [-o< [-o<
Last edited by larppaxyz on 04 Sep 2013, 18:53, edited 3 times in total.