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

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Northern_Mike

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Post by Northern_Mike »

addo wrote:Have you seen the suction pumps? They're all over Fleabay now, but about $120 here from memory. I've avoided buying one thus far. A benefit of them, is they're graduated in litres so you can see how much is removed.
I have one. It's great. I bought it originally to use on a 306 which someone had absolutely ruined the sump plug on. Works very well. Great for removing LHM/brake fluid/coolant too. It's a Sealey one, cost me £40-odd, but well worth it.
addo
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Post by addo »

I'd love one, but funds prescribe otherwise. I have some vet syringes and clear PVC tubing for siphoning stuff up.

A siphoning pump would be awesome when I've overeaten, too. Just poke the tube down your throat and Bob's your uncle.
Northern_Mike

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

Post by Northern_Mike »

I have one just like this.

http://www.amazon.co.uk/diy-tools/dp/B000RA16CO" onclick="window.open(this.href);return false;
isisalar
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by isisalar »

I recently got a less sophisticated version a bit like a beefed up bicycle pump from my local motor factor's. It cost about a tenner and empties the LHM tank in about 8 sucks.
Cheers
Paul
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

isisalar wrote:I recently got a less sophisticated version a bit like a beefed up bicycle pump from my local motor factor's. It cost about a tenner and empties the LHM tank in about 8 sucks.
Cheers
Paul
Paul that sounds ideal, can you remember where you got it or what brand it is ? I can't afford £40 or more for something I only want to use once at the moment, but I can afford a tenner and it would be a useful thing to have around. :)
larppaxyz
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by larppaxyz »

Hi, few weeks ago i told that everything is running fine after fiddling with knock sensor wires. Well, issue came back and i can't get rid of it again. I'm pretty sure, knock sensor mapping are messed up again and unplugging battery would get thing back to normal for a while. Earlier i said i have absolutely no tappet noises, but i was wrong. I don't know what s**t oil was poured to my engine but after last oil change i do have it when starting up cold. I think that noise could be enough to confuse knock sensor. I'm going to take apart it once more, check all wiring and disconnect battery. We see what happens, on my case it's very easy to notice if car runs fine or has it bad days. I can tell immediatly when i switch it to gear or listen how it idles.

Oh... and this problem has nothing to do with exhaust or oxygen sensor, i have most of exhaust and oxygen sensor replaced not too long ago and they made no difference. My cat works fine and is not glogged or rattling.
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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:Hi, few weeks ago i told that everything is running fine after fiddling with knock sensor wires. Well, issue came back and i can't get rid of it again. I'm pretty sure, knock sensor mapping are messed up again and unplugging battery would get thing back to normal for a while.
Sorry to hear your problem is back again, I know how frustrated you must feel! :?

I agree that it is the knock retard table being semi-randomly filled with large (possibly maximum) retard values due to excessive knock sensor activity, however I don't yet know why its happening, whether its actual knocking, (lean mixture perhaps) "false knock" due to excessive mechanical noise from the engine, (such as noisy tappets, rattles in the engine bay etc) a faulty sensor, or an electrical problem like wiring, although I think I have ruled out the harness side wiring from knock connector to ECU connector on mine - it tests fine, so if there is a wiring fault its between the knock connector and the sensor itself. (Impossible to confirm without stripping down the engine and replacing the knock sensor) It could be any one of the above although I am leaning towards an actual mechanical noise.

As you say, resetting the ECU by disconnecting the battery for 15 minutes improves the performance for a while sometimes dramatically particularly if the engine is already warmed up. As far as I know on the Bosch MP7.0 the only data that is lost during a power supply reset are the fuel trim and knock retard tables, I don't think its long term fuel trim related as the lack of power also exists in closed loop mode when the oxygen sensor is controlling the mixture. (Incorrect saved long term fuel trim is only really going to cause problems in open loop mode as in closed loop short term fuel trim can counteract any error in long term trim and will eventually correct it as well as the ECU learns)
Earlier i said i have absolutely no tappet noises, but i was wrong. I don't know what (-expletive removed-) oil was poured to my engine but after last oil change i do have it when starting up cold. I think that noise could be enough to confuse knock sensor. I'm going to take apart it once more, check all wiring and disconnect battery. We see what happens, on my case it's very easy to notice if car runs fine or has it bad days. I can tell immediatly when i switch it to gear or listen how it idles.
How long ago was the oil change ? Do you mean your tappets are noisy to begin with and then quieten right down after a few minutes or do they remain noisy ?

What happens if you start the engine but let it idle for a few minutes until the tappets are quiet and then drive, is the performance ok then ? I'm finding that mine runs much better if I wait for the engine to warm up a few minutes before driving.

If it is noisy tappets being picked up by the knock sensor it makes sense - cells in the knock retard table are only updated in the presence of "knock" if the engine is currently at the given rpm/load combination. If the engine is kept at idling speed until it is "quiet" then no knock retard cells above idling rpm can be filled in with false retard values...

However if the car is quickly driven away and revved under load whilst still noisy the ECU hears a lot of noise and starts filling in retard values in many cells across the engines working rpm and load ranges creating "flat spots" in the performance curve. Once those erroneous retard values are filled in in many cells it takes a long time for them to be gradually reduced by driving through the same rpm/load combinations while the engine is quiet. In my experience this can take days or more, whereas an ECU reset is immediate.

Try what I suggested, reset the ECU, then let the engine idle for several minutes without revving when starting from cold, see if the performance is good during that driving session, if so it may point towards mechanical noise pickup, noise which is worst when the engine is cold.
Oh... and this problem has nothing to do with exhaust or oxygen sensor, i have most of exhaust and oxygen sensor replaced not too long ago and they made no difference. My cat works fine and is not glogged or rattling.
Thanks for confirming your exhaust is in good condition. I've long ago ruled out exhaust as the issue, it just doesn't fit the symptoms, not to mention I've done a back pressure test with NO measurable back pressure.

I have a couple of ideas to try to narrow this down problem further:

One is I'm going to try the Lubegard engine oil additive to see if it will further quieten down my tappets:

http://www.lubegard.com/~/C-180/LUBEGAR ... Protectant" onclick="window.open(this.href);return false;

Two or three are still quite noisy and have actually got noisier since my engine oil change compared to how they were with the old oil with wynns hydraulic lifter additive added. I believe that most of my tappets are silent but 2-3 are intermittently noisy. Before the original wynns additive was added ALL tappets were noisy, all the time, and there was a definite improvement in consistency of performance almost immediately after the additive quietened down the tappets.

My second idea is to measure the knock sensor signal on a scope and also try temporarily "desensitising" the knock sensor just a small amount with resistors, not too much so as to risk damage to the engine or put the ECU in fallback mode, but enough to see if there is a correlation between reduced knock sensor activity and increased and/or more reliable performance. If I can prove a correlation between knock sensor input and loss of performance then at least we know we are looking in the right direction.
isisalar
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by isisalar »

I knew that the Lubegard gearbox stuff would help with those issues and although I've never used it, I'd be pretty confident the tappet treatment would be similarly effective.
Wouldn't it be ironic if the longest thread in history was killed off with two bottles?
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Paul
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Ironic but infuriating if that was the case Paul :twisted:

The lubegard has arrived already =D> Now all I need is a not raining day to syphon out some oil and put it in... :roll:
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Incidentally, in case it's eventually found to be a faulty knock sensor, I just stumbled across some good dismantling pictures of the ES9J4:

http://peugeot605.forumeurs.fr/remplace ... t2894.html" onclick="window.open(this.href);return false;

In the third picture down in that thread you can see the lower intake manifold removed revealing the knock sensor (the small black circle with a bolt through it just to the left of the black and red connector near the middle of the V block:

Image

Doesn't actually look nearly as hard as I thought to get to. Over and above the standard removal of the upper inlet manifold (which is a half hour job) it doesn't look too difficult to remove the lower inlet manifold to access it, as shown in the picture.

It's a bit more obvious where it is in this later picture with the heads removed, although the heads don't need to be removed to get to it! :twisted: :lol: It can be seen near the centre of the block with the black cable and green connector:

Image

The lower inlet manifold gaskets are a bit on the pricey side at around £30 from memory, with the knock sensor actually cheaper than the gaskets at around £20... :roll: after seeing these pictures I'm fairly confident that I could replace the knock sensor if I really had to, so that cheers me up a bit. :) About £50 and a good few hours work maybe but nothing I couldn't manage.
Last edited by Mandrake on 02 Jul 2013, 23:20, edited 1 time in total.
larppaxyz
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by larppaxyz »

Mandrake wrote:
larppaxyz wrote:Hi, few weeks ago i told that everything is running fine after fiddling with knock sensor wires. Well, issue came back and i can't get rid of it again. I'm pretty sure, knock sensor mapping are messed up again and unplugging battery would get thing back to normal for a while.
Sorry to hear your problem is back again, I know how frustrated you must feel! :?
Yeah, luckily i have some other things to worry also and i have had this issue for years. This time car was fine around two weeks.
Mandrake wrote: I agree that it is the knock retard table being semi-randomly filled with large (possibly maximum) retard values due to excessive knock sensor activity,--- snip ---
It could be any one of the above although I am leaning towards an actual mechanical noise.
Yes, i'm starting to lean towards mechanical noise too. I don't belive it's real pinging that knock sensor is detecting.
Mandrake wrote: How long ago was the oil change ? Do you mean your tappets are noisy to begin with and then quieten right down after a few minutes or do they remain noisy ?
Oil change was around two months ago.

After car sitting overnight and i start it up, there are tappet noises for around 10-15 seconds. I can't hear them inside car, so i was bit suprised. When car is warm, there are no tappet noises.

I don't let car idle after starting up, i almost immediatily reverse out from my parking spot and off i go. There is also this annoying thing that as gearbox is still cold, it doesn't shift until >3000 rpm (for first 120 seconds) and as it's a slow and tiny road for few hundered meters, i pretty much run it at around 2500 rpm's. This is the 'cold gearbox' mode descripted in gearbox technical manual.
Mandrake wrote: What happens if you start the engine but let it idle for a few minutes until the tappets are quiet and then drive, is the performance ok then ? I'm finding that mine runs much better if I wait for the engine to warm up a few minutes before driving.
If this issue is ON, it doesn't matter if it's cold or warm. You can't get rid of it anymore.
Mandrake wrote: If it is noisy tappets being picked up by the knock sensor it makes sense - cells in the knock retard table are only updated in the presence of "knock" if the engine is currently at the given rpm/load combination. If the engine is kept at idling speed until it is "quiet" then no knock retard cells above idling rpm can be filled in with false retard values...
Yes, however, knock sensor should not pick up something like noisy tappets... but who knows.
Mandrake wrote: Try what I suggested, reset the ECU, then let the engine idle for several minutes without revving when starting from cold, see if the performance is good during that driving session, if so it may point towards mechanical noise pickup, noise which is worst when the engine is cold.
I did what i did last time, disconnected battery, disconnected knock sensor once, fiddled with earth cable.

And as i was expecting, issue disappeared. I only had battery disconnected for around 45 seconds. So, resetting ECU fixes it for me (for a while).
Mandrake wrote: My second idea is to measure the knock sensor signal on a scope and also try temporarily "desensitising" the knock sensor just a small amount with resistors, not too much so as to risk damage to the engine or put the ECU in fallback mode, but enough to see if there is a correlation between reduced knock sensor activity and increased and/or more reliable performance. If I can prove a correlation between knock sensor input and loss of performance then at least we know we are looking in the right direction.
I'm thinking about something like this too. I'm not sure if it can be done with just resistors, but with oscilloscope you should see what needs to be done :)

Maybe replacing knock sensor is only way to be sure it's not electrical failure. Least i have pretty much replaced every other sensor
.
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

larppaxyz wrote: Oil change was around two months ago.

After car sitting overnight and i start it up, there are tappet noises for around 10-15 seconds. I can't hear them inside car, so i was bit suprised. When car is warm, there are no tappet noises.

I don't let car idle after starting up, i almost immediatily reverse out from my parking spot and off i go. There is also this annoying thing that as gearbox is still cold, it doesn't shift until >3000 rpm (for first 120 seconds) and as it's a slow and tiny road for few hundered meters, i pretty much run it at around 2500 rpm's. This is the 'cold gearbox' mode descripted in gearbox technical manual.
I have the same problem where I'm living at the moment, the "depollution" program in the gearbox holds 1st gear for a full 2 minutes because I can't go fast enough to exceed 3200 rpm in 1st in the narrow windy streets until reaching a main road. The only way to override this is to engage 2nd gear manually by selecting snow mode and selecting 2nd gear. (In snow mode 1st, 2nd, 3rd manually select a gear even forcing an upshift at low speeds)
Yes, however, knock sensor should not pick up something like noisy tappets... but who knows.
Normally I would agree, but look in those pictures how close the knock sensor is to the inlet valve gear on this engine, because its mounted at the top of a high V block. On 4 cylinder engines the knock sensor is usually a lot further from the valve gear half way down the side of the cylinder block.
I'm thinking about something like this too. I'm not sure if it can be done with just resistors, but with oscilloscope you should see what needs to be done :)
I can't see why it wouldn't work, it might require an L-pad (series and shunt resistors) or depending on the impedance of the piezo and how the ECU detects a faulty sensor the right value of shunt resistor in parallel may be all that's required, avoiding cutting any wires. I won't know until I try.

I'm going to try the Lubegard first though.
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Stempy »

Mandrake wrote: I'm going to try the flushing agent and the additive to see what happens. If that does nothing then I might admit defeat...

Or you could just buy this one

http://www.ebay.co.uk/itm/221248537552? ... 1423.l2649" onclick="window.open(this.href);return false;
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Post by addo »

Didn't that 605 owner tear down the motor in some rapid timescale? From memory he was pretty casual in his writeup but didn't faff about in the work.

I think the V6 knock sensor is largely where it is, for reasons of practicality - outside the block it would be perilously close to exhaust heat. Failures across the internet seem very uncommon.
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Stempy wrote:
Mandrake wrote: I'm going to try the flushing agent and the additive to see what happens. If that does nothing then I might admit defeat...

Or you could just buy this one

http://www.ebay.co.uk/itm/221248537552? ... 1423.l2649" onclick="window.open(this.href);return false;
But I've gone off Series one styling now after a year of Series 2 ownership... :lol: I'd forgotten how different the dash instruments are too...and the front is just too blunt looking... :twisted: I also don't like silver so if I replaced this one I wouldn't be wanting another one in silver...

Seriously though, 71K is nice, but... London...couldn't really be any further away. No where (literally) for me to put it even if I could get it back home, nowhere to work on it to do the inevitable work that needs doing etc...

While we're staying with the inlaws buying another car is a non starter unless this one outright spits the dummy and dies on us. Lets face it, I'm unhappy that it isn't performing as well as it should be but it drives us from A to B and touch wood, aside from the broken exhaust (that could affect any old car) and the minor banjo leak it hasn't really let me down in a "can't drive it" way yet, despite all of the niggles I have. As far as my other half is concerned the car works fine so she doesn't understand why I'm always tinkering with it... [-X Selling an apparently (to her) working car and buying a fresh load of trouble would not go down well when we're saving for a house. :twisted:

When we get settled into our own house again with hopefully a garage or at the very least a drive way, then I may go on a fishing expedition to see what other V6's in better condition are available, but not just now. With a bit of luck by then David will have completed his V6 Activa conversion and already got bored with it... :twisted:
Last edited by Mandrake on 03 Jul 2013, 15:31, edited 2 times in total.