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

[Hell Razor5543]

In my experience, while coincidences happen, they don't happen often. I'd check that cat (give it some Whiskers!). The timeline suggests it is a good starting point (and if it was hot at the time, it is more likely to have broken).

[Mandrake]

Also worth mentioning is that we did 800 miles of touring over a period of about 5 days around 3 weeks BEFORE the MOT. The car ran perfectly on that trip, including no apparent gearbox problems, then everything started to go pear shaped just over a month later...

[Mandrake]

One other thought has popped into my head regarding (seemingly) low engine output power when warmed up, looking back through my Lexia data earlier in this thread I notice the coolant temperature reading when warmed up was as high as 97 degrees - is there any engine ECU strategy where it will deliberately limit engine output power if it is too hot ?

It could do so by retarding timing (like it does when the gearbox commands it to during a gearshift) or possibly other ways. Anyone know if there is any self protection power limiting strategy in the ECU ? (Or know of a training manual for the engine ECU I could download) Come to think of it the lack of power when hot does feel a lot like retarded timing...

Anyone know if a Lexia reading of 97 degrees is too high ? If so I'm assuming its either a faulty sensor giving that reading, or it is running too hot possibly due to a sticking thermostat. Is checking the temperature and ignition timing on live data worth exploring ?

[addo]

When the exhaust is blocked, coolant temperature rises - especially under load.

The contents of converters are quite brittle, and shock will break them - you only need it to form a few large chunks such that one can jiggle around and block inflow, and you're in strife. Can you test with a decat pipe?

[Mandrake]

Thinking about the timeline more, and forgot about this thread:

http://www.frenchcarforum.co.uk/forum/v ... =3&t=41141" onclick="window.open(this.href);return false;

I first posted about the groaning noise which we now believe to be the gearbox on the 7th of September, saying I had been noticing it for "a few days", so lets say around the start of September. The exhaust broke (and thus started this thread) on the 14th of September, a full 2 weeks later, therefore the groaning noise predates the exhaust breaking.

The 800 mile trip was early August and the MOT on the 18th of August. So from no real problems in early August to gearbox groaning at the start of September...

[Mandrake]

When the exhaust is blocked, coolant temperature rises - especially under load.

The contents of converters are quite brittle, and shock will break them - you only need it to form a few large chunks such that one can jiggle around and block inflow, and you're in strife. Can you test with a decat pipe?

Hmm. Can't really test that at the moment. The problem with this line of enquiry is there is no point spending money on a cat when we don't know if gearbox failure is imminent...

Also the power loss does seem to be intermittent. After changing the plug leads it was initially very good even at low revs although it then deteriorated when fully warmed up. I would have thought a damaged or blocked cat would result in a permanent loss of power, not one that varies from hour to hour and day to day.

[addo]

I'm referring to the straight through "test pipes" you can buy for a few models. Can't see one listed for a V6 so you may be looking at a gutted cat to play with instead.

My own observation with a failing converter was, the performance drop is intermittent - looking back it may have started three years ago.

[CitroJim]

Is there anything inside it that would be brittle that might have been damaged by a sudden jolt like that ?

Yes, it has a ceramic honeycomb inside and it's quite delicate. A bad knock will certainly shattter it and cause a blockage. The can be killed by a backfire too which is why it's dangerous to run a cat car with a misfire; if enough petrol vapour gets in the cat it can go bang and then it's by-bye cat...

[Mandrake]

Drove to work this morning, very wet misty conditions, the performance of the car was absolutely GUTLESS. My old 2 litre would have put it to shame. No misfiring as such or rough running, just no oomph or throttle response both when it was cold and no real change as it warmed up. Just completely flat performance. On the way home it was a bit better but not much, when trying to pull away from a roundabout and climb a slow hill it was shuddering and making a right meal of it, the gearbox was searching up and down for a gear, just terrible really. Not in the least bit smooth or drivable like a V6 ought to be.

I thought I'd fixed an important problem with the spark plug leads but in these wet conditions its honestly no better than before! Yes, I've rechecked the old spark plug leads and two of them are indeed open circuit, so there is no doubt they were faulty and in need of replacing.

I really am in despair again, what I don't understand is how rapidly so much has gone wrong despite doing my best to fix things and despite so much help from the forum. I feel like I'm bailing out a sinking ship and I'm still going under...

When I bought it in March the engine performance was terrific, I remember accidentally spinning the wheels from a standing start on several occasions when I first took it home (yes it was raining) as it was so zippy and I wasn't used to the highly responsive throttle. The gearbox apart from a bit of occasional hunting for the best gear was smooth and quick and quiet with no apparent issues, no slipping, no groaning, no shuddering etc.

Right up until early August I had no complaints with either engine or gearbox (yes, a lot of other work needed doing) and we did an 800 mile trip in early August where it went like a little rocket, I couldn't be happier, and then since late August its been problem after problem to the point where its taking the p**s out of me and both engine and gearbox have gone down the tubes so rapidly that I can't figure out what the heck is going on and why its happening. The more problems I find and fix the worse off I seem to be! I'm in serious trouble with my other half now for the amount of time, money and parts that have gone into it since August, its now to the point where she's wanting me to get rid of it, and I really can't blame her...

So now we think maybe the cat could be damaged and have loose chunks floating around inside it that are sometimes blocking the flow ? Could this explain intermittent flatness in performance though ? Where it can go from very zippy and almost normal to just a few hours or days later being absolutely flat and gutless ? My problem with this theory is that often in a 20-30 minute drive the first 10 minutes the car will be almost normal, responsive and zippy, by the end of the drive its totally gutless. I also don't see the connection to dry or wet days - on very dry days it runs quite well, on wet days its gutless. How could a broken cat cause this ?

If there is a problem with the cat as well that's a mountain too far, I wouldn't mind chancing my luck on a 3rd party cat if the gearbox was good but with the gearbox seemingly pretty much stuffed and hanging on by a thread I really can't throw any more money after it. I think I'm seriously going to have to call it a day and admit defeat with this car. I've given it my best but I just can't get to the bottom of its problems within the resources and time I have, and as I have the ever looming spectre of gearbox failure hanging over my head I can't put much more money into it apart from petrol.

I still would like to catch up though David so I can get a chance to see what a V6 should drive like when its working properly!

Thanks for your help everyone, I wouldn't have got this far without it.

[Mandrake]

Cold dry air again tonight driving home, engine performance is right back up to normal(ish). Above 2000rpm it was very zippy and responsive, you wouldn't even think there was anything wrong with the car above 2000rpm tonight.

Also pulling quite well below 2000rpm, although the gearbox is misbehaving under load at those low revs..eg some shudder and funny noises etc... but the engine still seems quite responsive despite it.

Surely the cat cant be to blame if it consistently runs well in dry air and poorly in damp air ? The coil pack, spark plug leads and spark plugs are all new, can anyone think of anything else that might cause it ? Could it be something as simple as a MAP sensor ? There has to be some explanation for this...

[Xantidote]

Hi Simon,

I've no magic suggestion for you, but you've previously mentioned that engine performance seems to be weather related. Maybe some circuit/ecu is breaking down in humid/moist/wet conditions, or it's temperature related. You've had no leaks into the car or engine bay, or damp/wet areas wherever the ecus, or multi-plug connectors, are located? Just a thought - water and electronics aren't happy bedfellows.

[Mandrake]

Thanks Martin,

I didn't actually think about water leaks into the engine bay...it was absolutely bucketing down today (I think we had about 20mm predicted) so I popped the bonnet open after a heavy spell but everything seemed dry, so I don't think rainwater is getting into the engine bay. Funnily enough the engine ran rather well today despite all the rain, just to add confusion to the mix...it seems to relate more to ambient humidity, and actual rainfall and temperature don't seem to matter much.

[DHallworth]

Simon,

Do you have other means of transport or is the Xantia your only means of getting to and from work?

If you can live without it for a few days then feel free to bring it over here and leave it with me if you want. The handy thing about having another and some time is that I can try swapping sensors between them and see what's going on with yours.

We had problems off our S1 generally being a pain in the arse and it turned out to be one of the coolant temperature sensors. Basically it was causing the car to run on choke and it was spluttering and running rough. Economy was bloody awful too!

I can give you a lift home after you've dropped it off if you wish or could even pick the car up with the trailer I guess.

I'll PM you my telephone number, feel free to give me a shout if you want, sometimes helps just having someone else to bounce ideas off.

Regards

David.

[Mandrake]

Hi David,

Thanks for the offer, I was going to PM you shortly as it happens. Quite a bit has happened in the background since I last posted in this thread, so I better bring people up to speed.

Regarding the poor running of the engine, it seems to have miraculously fixed itself! The engine itself has been running great since my last post, whether dry or wet, no problems with the performance over 2000 rpm, nice and zippy and responsive, although not having driven another V6 I don't know if it is 100% of normal or just 80% of course... but certainly nothing like the dead flat performance that I have seen at times recently.

Given that I have previously replaced the coil pack, spark plug leads, spark plugs, fixed a missing inlet manifold gasket and currently have the oxygen sensor disconnected (ruling it out) my current working hypothesis is that I have an intermittently dodgy MAP sensor that has decided to play nice in the last few days. I can't really think of anything else that could cause a large loss in power that could come and go away within a day... my gut feeling is it isn't the catalytic converter being blocked either. I don't think its the coolant temperature sensor, every time I've checked the reading from that on the Lexia it has seemed accurate.

Of course all of this is a moot point if the gearbox is on death row....on Saturday I decided to do a second change of LT71141 on the basis of "what do I have to lose", having already bought the oil. The first change a few weeks ago came out filthy dirty and didn't seem to improve the groaning noise, if anything it got a bit worse after the first change.

The second change I did this last Saturday appears equally dirty to the naked eye when compared side by side in bottles, however the very next day and just a few miles driving I noticed an improvement in the gearbox, I went for a short drive to the local shops and for the first time I can remember in a couple of months it didn't groan at 1500 rpm pulling up the hill on the way home. This morning I got all the way to work (only about 10 minutes and 1 mile to be fair) without a single groan from the gearbox, and I deliberately tried to provoke it by giving the accelerator a good poke at low revs but not enough to cause a kick down. No groaning. On the way home the same again - I got all the way home including pulling up a steep hill at 1500rpm without it groaning even though I tried to provoke it, however I decided to do once more around the block to let the car finish warming up (the symptoms are always worse when the gearbox oil is hot) and it DID give a small groan or two the second time up the same hill, but only when I tried to provoke it.

The engine seemed to pull much better below 2000 rpm when its not groaning as well, leading me to believe that the gearbox may be signalling torque reduction to the engine ECU when the problem is occurring.

So its certainly not fixed yet but the second oil change seems to have made a substantial improvement, this is the first time since the symptoms appeared in early September that they have actually started to regress. Encouraged by this I will be doing another change or two as soon as I get the chance, and I have some theories on what might be causing the problem as well...

In answer to your questions, yes the Xantia is my only means of transport to work, other than a half hour walk, although I won't be at this job too much longer. (Still waiting on a starting date for my new job, grr)

Even though the engine itself seems to be running a lot better now I would still like to come and visit to swap notes etc...it will be nice to see another V6 and get an idea of how they should run, and also for you to observe the behaviour of mine...not to mention meet another FCF regular

I'll send you a PM shortly to see if we can find a time for me to come visit. Roughly how far away are you ? I'm in Coatbridge...

[DHallworth]

I've got a friend who has a Range Rover with the 5HP24 gearbox in it. That also runs on LT71141.

He took it to Mackie's Transmissions in Glasgow and let them do a "Hot Flush" on the gearbox and says that the difference is unbelievable. Apparently this is the only way to be 100% sure of getting all the dirty fluid out.

David.