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

[Mandrake]

I reckon I can have this car fixed by page 100

Promise?? Certainly hope so, as you deserve it for all the time and effort you've put into it. Perhaps sorting the engine's become a challege you can't give up on

It has become a bit of a challenge I suppose, I don't like to give up on things easily.

Part of the reason is as I read the forum it reminds me just how good the mechanical condition of the rest of the car is now that I've sorted the initial few things last year like spheres, handbrake cables, droplinks etc..

Apart from a big scratch across the bonnet (which could be solved with a bonnet swap) and the odd nick here and there, the rest of the car is mechanically and functionally in pretty good shape.

Nothing is broken and everything electrical/mechanical works except for the drivers seat heater. I keep reading about other Xantia's (including V6's) struggling with things like leaking/rusted/burst hydraulic lines, leaking heater matrix / split heater matrix elbows, seizing brakes, seizing height correctors, malfunctioning central locking or power windows, leaking windows, dying alternators, problems starting in the cold weather, failing engine mounts etc etc, with some people having problem after problem crop up... touch wood I've had none of these problems, the car starts first time, rides well, handles well, and feels nice to drive.

The only recent problems I've had (ignoring the engine issues) have been a slight leak on the hose at the hydraulic pump and my battery clamps both splitting and giving out on me. It flew thorough the last MOT with no advisories despite me not doing any significant non-engine related work on the car this year. The only spectre on the horizon is whether or not I'm going to need a new cat next year - the marginal emissions reading could be a dead cat or it could be due to the misfire it had when it went in for the test...

If I can nail the engine performance issues she's a pretty nice car.

If I gave up and sold it and bought another V6 the engine might be running properly but I could let myself in for a world of hurt on all the other mechanical issues that this car doesn't seem to have. Just look at all the work Trainman is having to do on his outwardly nice looking and cared for V6!

[myglaren]

Re: the cosmetic damage to the paintwork, we were recently approached by Dr Colour Chip with a view to promoting their products on the forum.
As everyone knows we won't accept advertising on the forum nor affiliate ourselves with any commercial enterprise.
However, I do have a link to their website if you would be interested in more info about their product.

I can't make any recommendations as I know absolutely nothing about the company or the product.

[larppaxyz]

I promise to swap my TPS before this thread hits 100 pages

[lexi]

Anyways, the musical sparkplug trick.

[Mandrake]

I promise to swap my TPS before this thread hits 100 pages

Me too.

All going well I will be fitting it this Sunday. Even the chatterboxes shouldn't be able to push it past page 100 before then. Fingers crossed it makes a difference too...

[Northern_Mike]

I promise to swap my TPS before this thread hits 100 pages

Viewing from Tapatalk, it's already 138 pages.

[Mandrake]

I promise to swap my TPS before this thread hits 100 pages

Viewing from Tapatalk, it's already 138 pages.

Sorry, not admissible as evidence.

Oh wait. I get it, by even replying I'm working against my own objectives...

[CitroJim]

We can lock this thread for you Simon - that'll stop it going over 100 pages

[larppaxyz]

Bah, tried to order TPS from german and UK ebay's and they don't ship here. So, i must go to local dealer. Would have been much easier to just order it online.

[Mandrake]

You don't want to be getting one from a dealer as they want well over £100!

If you can't find one cheaply let me know.

[Mandrake]

Well guys I got the TPS changed over before this thread hit 100 pages. Is the car fixed though ? We shall see...

Thanks to lexi for his help and car port (and cheese sandwiches and many hot cups of tea ) on Sunday the plug leads and TPS were changed over. It turns out there was something, possibly thread lock in the bottom TPS bolt as I suspected - I would never have got it out in-situ on the car, it was a struggle to remove it without stripping the head even with the manifold out in my hands and a torx driver pushing down hard on the screw head, in fact we had to run a tap through the hole to clean out the thread afterwards, but everything was fine after that.

As always the spark plug leads were a bit of a brain teaser to figure out exactly where to align the new leads within the top plastic guide so that there is enough length on either end... they REALLY don't leave any slack in these cables, especially the front left cable which only barely reaches at both ends...

Got it all back together and.... the stumble when I flick the throttle off idle is still there. No change to that symptom at all after replacing the TPS... On a test drive though the car was running exceptionally well, very responsive on the throttle, loads of power etc. It stayed like this all the way home on the motorway and I then did my usual test circuit of roads after getting home and it was running brilliantly then too, no complaints except that stumble flicking the throttle at idle.

Since Sunday the car has only been driven for 5 minutes at a time in mostly near zero conditions on slippery roads so I've had no chance to see whether performance has remained excellent or has deteriorated again. (The battery was off during the work on Sunday, therefore resetting the ECU which sometimes leads to short lived improvements...) It starts on a dime first time even at -2 degrees, although I've never had any cold starting problems with this car, except that my ECU seems to need to crank a few revolutions before firing on a cold start while this ECU fires instantly on the first revolution.

The loaner ECU is still in so I'm planning to leave that in about a week and give the car a good drive next weekend to see how it's running with this ECU, then another drive after swapping back to my ECU to see if there is any difference in ECU's.

So given its past cantankerous behaviour nothing is proven yet, it seems to be running well bar the hesitation when flicking the throttle off idle, so its just a waiting game over the next week or two to see how it behaves. Fingers crossed...

Either way, I won't be doing any more non-urgent work on it until after the winter. (apart from swapping ECU's back which is 5 minutes work) If the performance is still a bit erratic in the mean time I'll just have to live with it until winter has passed...

[Xantidote]

mostly near zero conditions on slippery roads

Yes, winter is nearly upon us, alas, though here in the northwest and close to the Irish Sea, it's nothing like as cold as it is with you. I guess we all hope our chariots will not give us problems through the winter months. Good to read that the car's running very well ATM, albeit with the odd hiccup. Maybe you're getting there?

Is your car out in the open, so all work done outside? . At one time you were talking of house/flat move, as I recall.

[Mandrake]

We've been down to -4 during the night the last couple of nights and I've needed to scrape the ice off the car the last two mornings as well - for the first time this winter. Yes unfortunately all work is being done outside on the side of the road at the moment, and it's going to stay that way until next spring...so use of lexi's car port was gratefully appreciated.

Regarding the stumble when snapping the throttle, I've just remembered something - when we finished reassembly I started the engine and ran it for a few minutes before re-fitting the air filter box and I don't remember it stumbling during throttle snaps with no air filter box, but as soon as the air filter box was re-fitted its stumbling on throttle snaps again... but why ?

The air filter was replaced fairly recently so I wouldn't have thought it could be blocked...any ideas anyone ?

When the air filter box is right out the air temperature sensor is also unplugged which may alter fuelling etc... perhaps I should try it again with the filter box still fitted but the filter element removed, and also with the top of the air filter box removed completely but air temp sensor still plugged in so the ECU is not getting an invalid temperature reading.

[larppaxyz]

Regarding the stumble when snapping the throttle, I've just remembered something - when we finished reassembly I started the engine and ran it for a few minutes before re-fitting the air filter box and I don't remember it stumbling during throttle snaps with no air filter box, but as soon as the air filter box was re-fitted its stumbling on throttle snaps again... but why ?

I personally think that original airbox is too restrictive. Without airbox engine feels and responds much better. With pugs there is also issue with intake "sock" that goes from airbox to front (i have that "sock" removed).

Anyway, i installed my brand new TPS today. After traditional ECU reset, throttle (again) feels snappier and downshifts and kickdown are much more "there when you need them".

Edit: TPS is some noname brand from local store, looks similar to those listed on eBay. 28 euros.

[Mandrake]

Regarding the stumble when snapping the throttle, I've just remembered something - when we finished reassembly I started the engine and ran it for a few minutes before re-fitting the air filter box and I don't remember it stumbling during throttle snaps with no air filter box, but as soon as the air filter box was re-fitted its stumbling on throttle snaps again... but why ?

I personally think that original airbox is too restrictive. Without airbox engine feels and responds much better. With pugs there is also issue with intake "sock" that goes from airbox to front (i have that "sock" removed).

Interesting! What is the issue with the 406 air sock that you're referring to ?

Over 6 months ago I was considering the possibility that the air intake "sock" from the air box to the grill could be restricted by being crushed/collapsed, or perhaps blocked with mud and leaves, but short of removing the front bumper I can't see any easy way to access the front end of the sock or confirm that its clear and not crushed.

At the time I tried running it with the sock disconnected from the air box, which apart from causing induction "boom" with the throttle open didn't seem to make much difference, however in hindsight the main loss of power at that time was ignition misfire related, so perhaps it's worth trying again now to see if it has any effect on the throttle snap stumble.

The problem with running it with the air box completely removed on the Xantia, even during testing, is that the air intake temperature sensor is mounted in the air box on the line to the ICV so must be disconnected, which will put the ECU into a parameter substitution mode (a fixed nominal air temp is assumed) which will alter fuelling and timing etc...so you don't know how much change is due to reduced restriction and how much is due to the ECU not knowing the air temp.

I usually find that if I try to drive the car with the air box completely removed that performance for light throttle is ok, but wide throttle performance is quite flat, (and noisy! ) but I'm not sure if the lack of a valid air temperature sensor reading is the reason or whether it upsets the induction tuning due to the shorter induction path.

Anyway, i installed my brand new TPS today. After traditional ECU reset, throttle (again) feels snappier and downshifts and kickdown are much more "there when you need them".

Here's hoping that the TPS makes an improvement for you even though it didn't for me. Well, it didn't solve the stumble for me, but for all I know some of the intermittent loss in power and throttle response was the TPS, I haven't yet had any examples of poor/sluggish throttle response since it was replaced...