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

[CitroJim]

Interesting stuff Simon...

Have you tried re-initialising the auto-adaptives using the Lexia?

Worth a go perhaps. It won't do any harm.

A jerky 2nd to 1st change is a common event on most 4HP20s I've known. I've researched it and my conclusion is it occurs when the line pressure regulator changes from low to high pressure. High line pressure is active during selection of 1st or reverse and I assume this is to ensure the operated clutches are operated hard to ensure they can transmit the torque available and deployed in these gears. For the remainder, the pressure switches low and this appears to make the changes a tad softer.

I'd be interested if your reading of the training notes brings about the same conclusion.

[CitroJim]

Mike, interesting links indeed. I confess that's the first time I've seen those threads and most illuminating...

So, maybe worth doing an oil change then Simon...

Did I ever send you the how-to guide?

[Mandrake]

It occurred to me that when Stempy had a V6, he had problems with something he initially described as a misfire...

Here are links to some threads:

[...]

Was it a real fix?
Did you happen to end up with his car?

Don't know - was his silver coloured ? Is Stempy still about ?

So if I read his threads right the conclusion was the problem was solved with a change of gearbox oil ?

[Mandrake]

Interesting stuff Simon...

Have you tried re-initialising the auto-adaptives using the Lexia?

Worth a go perhaps. It won't do any harm.

Funnily enough thats what I was planning to do next after reading about it in the training manual. It seems that the auto-adaptive initialisation is normally only done once at the factory (or if the gearbox/ecu is replaced) to allow the ECU to "learn" the exact characteristics of the gearbox (I assume that means things like clutch/brake efficiencies, electrovalve sensitivities and so on) and that is that. Just like "sealed for life" oil they assume everything will be fine years later...

It occurred to me that if the characteristics of the gearbox changed enough with wear and age that would be equivalent to changing the gearbox to one with different tolerances, and that the original calibration that was learnt may be well out by now leading to poor gear changes and perhaps the limited slip mode not working accurately...

So yes I will definitely try that, possibly tomorrow.

[Mandrake]

Mike, interesting links indeed. I confess that's the first time I've seen those threads and most illuminating...

So, maybe worth doing an oil change then Simon...

Did I ever send you the how-to guide?

Yes you did thanks.

Looks like an oil change could be on the cards too, (perhaps followed by re-initialising the auto adaptives a second time with the new oil) I've done changes on the 4HP14 a few times before so assuming my gearbox has the dipstick I shouldn't have any trouble doing it.

[Citroening]

Don't know - was his silver coloured ? Is Stempy still about ?

We bought Stempy's V6 from him (Reg was "V6 BDR" from memory) and it was a very nice car indeed after a little bit of TLC (Exclusive Alloys fitted etc). It is now with a Xantia Enthusiast and that's how we got Roger's Sisters V6 back from him as he P/X'ed it against it!

The FCF car rota/roundabout keeps going around as I think he's a member on here, albeit not a regular poster!

I'll see if I can dig some pictures out of it - it looked very smart indeed!

[CitroJim]

So if I read his threads right the conclusion was the problem was solved with a change of gearbox oil ?

That's how I read it Simon...

Stempy had his for a very long time so it must have been solved. Yours is not his I don't think. You got yours from Lexi didn't you?

As far as I recall, Stempy's had a dead A/C compressor and was snapped up by Franklin's dad. Pass on what happened to it from then on.

I can't recall now where Lexi acquired his from.

EDIT 1: Just seen your two replies Simon. If you do a re-initialisation before changing the oil then do do another after changing it as the characteristics may change a tad.

EDIT 2: Thanks Franklin Good to hear Stempy's is still being loved. I'm still scratching my head as to where Lexi originally got it from

[Mandrake]

Mike, interesting links indeed. I confess that's the first time I've seen those threads and most illuminating...

So, maybe worth doing an oil change then Simon...

Thinking a bit more about Stempys posts, it does sound quite similar to my symptoms, (although possibly worse than mine) if a gearbox oil change fixed his, could it be something as simple as dirty oil preventing the torque converter lockup from disengaging reliably ?

He said he had no symptoms at all when deliberately inducing limp home mode (ECU fuse removed) and I'm assuming that not only does limp home mode lock it in 3rd gear, but it probably leaves the torque converter permanently active (no lock up) to allow the car to start moving in 3rd gear, like snow mode ?

[addo]

Didn't he get it from Big Jock D?

[xantia_v6]

Interesting stuff Simon...

Have you tried re-initialising the auto-adaptives using the Lexia?

Worth a go perhaps. It won't do any harm.

Funnily enough thats what I was planning to do next after reading about it in the training manual. It seems that the auto-adaptive initialisation is normally only done once at the factory (or if the gearbox/ecu is replaced) to allow the ECU to "learn" the exact characteristics of the gearbox (I assume that means things like clutch/brake efficiencies, electrovalve sensitivities and so on) and that is that. Just like "sealed for life" oil they assume everything will be fine years later...

It occurred to me that if the characteristics of the gearbox changed enough with wear and age that would be equivalent to changing the gearbox to one with different tolerances, and that the original calibration that was learnt may be well out by now leading to poor gear changes and perhaps the limited slip mode not working accurately...

So yes I will definitely try that, possibly tomorrow.

Under most circumstances the "auto-adaptive" adapts correctly to compensate for wear and (presumably) oil condition, but it may be possible that it adapts itself into a state where it misinterprets slippage and gets stuck with wrong parameters. In that case a reset would be a very good idea.

The Mk2 V6 that I had for a while had some difficulty with the auto-adaptive function, and the transmission parameters would vary significantly over the course of a few days, between having very soft changes, with noticable spin-up when taking off from rest, to having rather sharp harsh changes, so it certainly was continually adapting, it was just never happy with the result.

[Mandrake]

Under most circumstances the "auto-adaptive" adapts correctly to compensate for wear and (presumably) oil condition, but it may be possible that it adapts itself into a state where it misinterprets slippage and gets stuck with wrong parameters. In that case a reset would be a very good idea.

The Mk2 V6 that I had for a while had some difficulty with the auto-adaptive function, and the transmission parameters would vary significantly over the course of a few days, between having very soft changes, with noticable spin-up when taking off from rest, to having rather sharp harsh changes, so it certainly was continually adapting, it was just never happy with the result.

Yes the shift characteristics do vary on this car, sometimes quite good, other times they can be a bit abrupt and erratic, and whether it releases the lockup or not seems to vary.

On your Mk2 did you ever reset the auto adaptives and if so did it make any permanent improvement ? Did you ever do an oil change ?

Could it be that the hydraulics on your Mk2 were intermittently malfunctioning due to sludge build up affecting the operation of the valves, and the auto adaptive was trying its best to compensate for the constantly changing behaviour of the hydraulics ?

The solution for both cars may be a change of oil (or 2 over a period of time) to clean it out followed by an auto adaptive reset a few weeks later after things have stabilised.

[CitroJim]

Simon, just a silly thought. Is the autobox ECU receiving an accurate road speed signal? If it is not it may account for a lot.

I've been out in mine today and as a test I got it (with real old git driving) crawling along at 30mph with 1500 rpm on the tacho and the TC locked up. A bit of gas and the TC released and she pulled away like a train. 30 to 70mph time was very impressive maintaining moderate gas. I could repeat this test ad-infinitum from various speeds.

Do you reckon your TC may not be unlocking correctly? The lock/unlock/limited slip is controlled by reversing the flow and pressure of oil through the TC. Your theory of sludge in the valve block may hold good and is perhaps making the valves a bit sluggish. Also, it's not unknown for the springs to break in the valve block but when it happens the consequences are very obvious.

[Mandrake]

As far as I know the road speed signal is ok, although since its in RPM at the output shafts I'm not sure what the exact conversion ratio is to MPH.

Today we did quite a bit of driving - not test driving just normal driving through the city and motorways and it was absolutely terrible. So bad in fact I thought the gearbox wasn't long for this world and we'd be stranded

Same symptoms as before but much worse, and it even managed to make the awful groaning noise at 2200rpm - its never done it that high before. Drivability of the car was really bad, I was having to coddle it by using sport mode or manual downshifts to keep the revs up... the lock up seemed to be all over the place, seeming to let go and go back on again rapidly and randomly in the 1500-2500 rpm range. Just really weird intermittent behaviour and strange noises. I thought I even heard a slight high pitched whir/whine under load at 60mph on the motorway (that I haven't heard before) that went away lifting off the throttle but that might have been paranoia.

I have a horrible feeling that something serious could be going wrong with the gearbox and that I need to change the oil ASAP to try to salvage the situation...

When we got back home I did an auto adaptive reset and went for a longish test drive with a helper to watch the Lexia live data to see what the torque converter lockup was doing. To be honest I didn't notice much difference between before and after the adaptive reset, after a while I think the gear change smoothness has improved but it seems that the issue with the torque converter lock up is still there.

I made note of the state of the torque converter when the engine was struggling and groaning, at 1500rpm in third applying load on the throttle the lockup state was either firm or piloted, or alternating quickly between them. It seems that when I put my foot down it would go from firm to piloted for maybe a second then back to firm. Sometimes it would go from firm to piloted and stay in piloted, but I could not feel any difference in behaviour of the engine revs or pulling between firm and piloted under any circumstances, leading me to the conclusion that either the limited slip (piloted) mode is very subtle or it simply isn't working and the converter is still locked up in piloted mode.

In cases where it did work properly I could see it was changing from firm to open, so the open mode is definitely working, although the ECU seems to rarely switch to open mode in the circumstances where I'm having trouble, its nearly always in firm or piloted at these speeds and loads.

I confirmed with the Lexia live data that the throttle load signal from the engine to gearbox is working perfectly - it provides a 0 to 100% throttle position figure to the gearbox that is proportional to the throttle opening.

At 1500rpm in 3rd gear it was staying in firm or piloted mode (and causing the engine to labour) until I exceeded 60% throttle as shown by the Lexia. Only then would it finally either switch to full open mode or change down a gear, allowing the revs to climb above 1500.

So it seems that either the ECU is failing to switch to "open" mode (or change down) readily enough, or the "piloted" mode is not providing any slip - moderate throttle at 1500rpm (25-50%) does change mode from firm to piloted, however there is no apparent difference in slip from firm mode that I can observe, and it also seems that when there is shudder (that feels like worn engine mountings) the shudder most often occurs in piloted mode.

After good engine performance for a few days, performance at low to medium throttle was very sluggish today, (weather was VERY wet and cold with heavy rain and flooding on the roads) although higher throttle higher rev performance still seems fine, and performance on the later test drive seemed a lot better than earlier in the day.

On the way home as I turned into the car park (a slight up hill) it laboured the engine at 1000-1200rpm in 2nd gear in full lock up even though I increased the throttle to nearly 50% to try to get some pick up. That can't be right, surely it should switch to open mode or even down to 1st ? (I don't know whether it was in firm or piloted mode in that instance as the laptop battery had gone flat by then)

Feeling at a bit of a loss again. One problem ? Two ? More ? Things seem to be getting worse week by week, and I really do fear for the gearbox.

[CitroJim]

Simon, there's something very seriously wrong. Mine doesn’t labour at all at 1500rpm in top gear, let alone third. Gosh, a V6 can go practically everywhere without ever exceeding 2000 rpm and not show the slightest sign of labouring at all, TC open or not. V6 engines don't labour!

Mine cleanly accelerates from 1500 rpm always in any gear and any circumstance. I deliberately tried it today. Whilst I was not watching a Lexia to see when the TC opened I could but I'll need to enlist an assistant. If it will help I will.

I think, in light of what I said before, that the problem is with the engine rather than the gearbox. That groaning is odd though I have to admit. A fault on the engine will make it seem as if the gearbox is about to throw the towel in. Remember, the engine is designed to produce a lot of torque at very low revs and is carefully matched to the gearbox so any deficiencies in the engine will show up more from the gearbox than perhaps they would if it was a manual gearbox.

[Mandrake]

Well, I'm at a loss then. Engine, gearbox, or both, I can't figure it out.

I could do the rear plugs but it's going to be really difficult for me to find the opportunity to do them now between shifts and winter weather. If I do those and theres no change, I'm not sure what to try next with the engine.

On the other hand I'm really concerned about the gearbox oil condition given the really bizarre behaviour I observed today, and the apparent problem with piloted mode. Finally, I've still got a broken exhaust - my patch up job is hanging in there but I think its leaking a bit now and I don't want it to burn the end off the cat tail pipe before I can get it fixed...

(Can anyone suggest somewhere in the greater Glasgow area who might be able to fabricate and weld a new sleeve on the cat tail ?)

Struggling to try to prioritise which one of these needs attention first with limited time and money to invest in it. This car certainly seems to have needed a lot of TLC in the last few months with no end in sight...