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

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Hell Razor5543
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Hell Razor5543 »

Possibly a silly question, but as I don't know the layout of the V6 engine bay I will ask it anyway. Where is the air box, and is there a MAF type sensor and connector just after it (engine bound)? If so, is it possible that the wiring could be suspect at or near that connector? The reason I ask is that as you have had the air box out several times, maybe when you do the wiring "clears up" for a short time, but the vibration from the engine causes the wiring to open up again over time.
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

There's no MAF on this engine, it has a MAP sensor instead but it's bolted to the back of the inlet manifold near the firewall well away from the air filter box.

The inlet air temperature sensor is part of the the air filter box and is unplugged when removing the air filter box, there are also a number of connectors near the air filter box including the knock sensor, two of the coolant temperature sensors, and the TPS.

All the connectors have been cleaned, checked, and measured on more than one occasion, I haven't been able to find anything wrong with any of them.
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Hell Razor5543 »

I was more wondering about the flexing of the wiring.
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Hell Razor5543 wrote:I was more wondering about the flexing of the wiring.
Understood, I've checked as best I can for intermitent connections when the wiring is flexed but haven't found anything.
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

A bit more progress today. :)

A very enjoyable day visiting David Hallworth to pick up a loaner CPH and engine ECU - nice warm sunny weather and a nice drive, and predictably on the day that I visit the car decides that it's going to run fairly well. Not as well as it should be not bad enough for me to complain.

I also had my first ride in an Activa - David's immaculate dark Blue Series 2. :) I have to say I was very impressed, the Activa was everything I expected it to be, and then some. Apart from a rattly rear Activa ram bush that needs replacing the car was extremely quiet and smooth, the ride was better than I expected it to be and it had an extremely stable feeling at speed with no front/back pitching at all. (I notice a bit of pitching over undulations on mine by comparison that needs looking into)

The lack of body roll didn't really call attention to itself under "normal" driving, but at the first round about it was very obvious - going around tight corners felt more like playing a video game than driving in an actual car subject to the laws of physics. :twisted: Definitely on the "must have" list, albeit only as a second car thanks to horrific MPG. :wink:

A couple of interesting things were noticed while we were looking at and running my car - I was trying to demonstrate the stumble that it has when you snap the throttle open at idle and David who was standing in front of the engine bay at the time noticed that it was back firing through the inlet manifold into the air filter box. #-o You could see the flexible hose from the air filter box to the throttle butterfly expanding during the back fire, as well as hear a little pop...

So the question is, why is it back firing ??! :shock: Too lean under wide throttle ? Anything else ? At various times in the past I've noticed intermittently on the Lexia a lean oxygen sensor reading under wide throttle under load, could this be the same problem that's causing a back fire ? The fuel pump and fuel pressure regulator have both been replaced and ruled out, so that leaves what, the injectors or the control signal to the injectors ?

The second thing we noticed is that when the engine was revved while stationary that at about 3500 rpm (under no load) there was enough vibration to shake the steering highly visibly, and you could feel the vibration through the floor as well. :?

Surely a V6 should be smoother than that ? I had noticed that the engine hasn't been as smooth revving lately, would it just be a misfire causing that amount of vibration at 3500 rpm or could worn engine mounts or other problems contribute ? The steering wheel doesn't vibrate at 3500 rpm when driving.

Moving on, thanks to addo's excellent guide we had the CPH and engine ECU out of the donor car in no time flat. As David doesn't have the CPH confidential code for it yet we decided not to try to fit them to my car at David's as it would require removing the steering shroud and playing with the transponder antenna.

Of course as soon as I got home it was too tempting, :twisted: especially when it was unusually hot and sunny, so I decided to see if I could trick it into working in the mean time by taping one of the matching keys to the transponder antenna.

So out came my CPH (again very quick and easy when you know how) and in went David's. I'm not sure why I tried it, but I decided to try starting the car with the new CPH but with my original engine ECU to see how the immobiliser worked - only to find that it started without any complaints! :shock:

A bit more testing and I realised that my engine ECU is in fact unlocked! :roll: It will happily start with either CPH, and even if I unplug the transponder antenna on the ignition lock it still starts without complaint, not even a warning on the dashboard.

This is a rather interesting development because this is proof that my engine ECU has almost certainly been replaced in the past - why would anyone bother to unlock it if it was the original ECU ? It's also almost certainly not been replaced by Citroen, as they would not fit a hacked unlocked ECU, so it must have been replaced with a second hand one sourced through "grey market" unlockers... (or one from a scrappy that has been sent to an unlocker) So why has my ECU been replaced ? What went wrong with the original I wonder ?

I then swapped the engine ECU over and sure enough the immobiliser prevented the engine starting, so David's ECU is definitely locked. With the steering cowl off and transponder antenna removed and held close to a matching key the engine started fine. The key had to be within about an inch of the antenna and the antenna had to be held well away from my key, if both keys were close it didn't work.

I went for a longish test drive and predictably the performance was excellent, almost flawless. :roll: It started off very good and got even better through the drive, possibly due to the ECU learning the characteristics of my engine. (The engine was already warmed up and had done 70 miles earlier in the day by the time I swapped the ECU so engine warm up wasn't a factor in the change)

Particularly at higher rpm it was pulling very strongly and eagerly, and was performing a lot better than the earlier journey to and from David's on the old ECU.

Of course I'm not jumping for joy as its far too soon to draw any conclusions yet. By virtue of swapping the ECU I've done an ECU reset, and as has been shown over and over before an ECU reset often leads to a temporary improvement in performance that goes away after a couple of days, so it will be a good couple of weeks or more of good performance before I can start to draw any conclusions...

Hopefully the CPH code will allow me to reprogram my keys to match the CPH so that I can refit the glovebox and steering wheel cowl. I'm missing my cruise control as the lower steering cowl houses the cruise control stalk. :mrgreen: At least now that I have the cruise control stalk out I can try cleaning the contacts with some spray - now that I've seen it its obvious that anything squirted down along the stalk would not have made it into the switch itself.

So I will keep people updated on how it continues to drive with the different ECU, whether it goes back to its old tricks quickly or whether its a permanent fix.

I'd be interested to see if anyone has any thoughts on the popping / back firing in the inlet manifold and the vibration at 3500 rpm - I can't say I've noticed any stumbling or popping in the manifold when snapping the throttle since I swapped the ECU but it's hard to be certain...
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DickieG
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by DickieG »

Mandrake wrote:So out came my CPH (again very quick and easy when you know how) and in went David's. I'm not sure why I tried it, but I decided to try starting the car with the new CPH but with my original engine ECU to see how the immobiliser worked - only to find that it started without any complaints! :shock:

A bit more testing and I realised that my engine ECU is in fact unlocked! :roll: It will happily start with either CPH, and even if I unplug the transponder antenna on the ignition lock it still starts without complaint, not even a warning on the dashboard.
Maybe, maybe not as once the ECU/CPH has been unlocked by turning the key it stays unlocked for a fair old period of time, so before you get too excited try the new CPH in the morning and see what happens,,,,,
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

DickieG wrote:
Mandrake wrote:So out came my CPH (again very quick and easy when you know how) and in went David's. I'm not sure why I tried it, but I decided to try starting the car with the new CPH but with my original engine ECU to see how the immobiliser worked - only to find that it started without any complaints! :shock:

A bit more testing and I realised that my engine ECU is in fact unlocked! :roll: It will happily start with either CPH, and even if I unplug the transponder antenna on the ignition lock it still starts without complaint, not even a warning on the dashboard.
Maybe, maybe not as once the ECU/CPH has been unlocked by turning the key it stays unlocked for a fair old period of time, so before you get too excited try the new CPH in the morning and see what happens,,,,,
No I don't think so, mine is definitely unlocked. I had the battery off for over 10 minutes while I was swapping the CPH and it started first try. I then had the engine ECU out of the car completely for about 20 minutes while I tried the other one, then when I put it back it started again first try without having the correct transponder near the antenna.

David's ECU once started will start again without the transponder signal but only within about a one minute window, after the key has been off for more than about a minute it needs the transponder signal again. I didn't time it exactly but I confirmed this behaviour multiple times.

I'll try my ECU again tomorrow without a transponder after the ECU has been unplugged for 24 hours but I'm pretty certain it will start.
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

A couple of observations this morning with the new ECU.

For quite a while now (months at least, long enough that I can't remember when it started happening) although it always starts first time, the first start in the morning has taken a while to "catch". I'd say maybe 1.5 seconds worth of "dead" cranking before it will suddenly catch and start.

That's even if I turn the key on and wait a couple of seconds to let the fuel pump prime first rather than going straight from off to start. After the car is already warmed up it catches straight away when starting. I've been wondering for a while what is causing this as it wasn't always like this.

This morning it caught and started instantly on the first revolution of the engine, just like it does when warmed up. :) Could be a fluke I know, but maybe not. It also usually sounds a bit like its misfiring for the first 10 seconds or so after a cold start - not this morning.

The next thing I noticed is that after the first start in the morning as I leave the house and drive up hill it has had a tendency to struggle a bit below 3500 rpm up hill even in 1st then suddenly roar away when it hits 3500 - no such symptoms this morning, it pulled very well with no abrupt change at 3500, although this particular morning symptom was always quite intermittent so a sample size of one doesn't mean much.

The third thing I noticed is that right from starting the car was feeling nice and torquey low down with plenty of pull even with a cold engine. In recent times I have actually been nursing it slightly in the cold mornings by using snow mode combined with manually shifting 1st, 2nd, 3rd to keep the revs up a wee bit, otherwise it was bogging and struggling slightly.

This morning I just left it in normal mode and let it do the shifting and it had no problems at all and as I say felt nice and torquey with good pickup.

I know, I know, its only one day and murphys law says the problem will come back in a few days, but at least it has got off to a good start! :lol:

The failure to catch quickly first thing in the morning when starting is one symptom that never went away and has not been responsive to any of the other work I've been doing though, this is the first time its caught instantly on the first start of the morning for a long long time.

The slight stumble/dip in rpm (and possibly inlet backfire) when opening the throttle suddenly from a stand still is still there however, but I now have an idea what that might be...
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

DickieG wrote:
Mandrake wrote:So out came my CPH (again very quick and easy when you know how) and in went David's. I'm not sure why I tried it, but I decided to try starting the car with the new CPH but with my original engine ECU to see how the immobiliser worked - only to find that it started without any complaints! :shock:

A bit more testing and I realised that my engine ECU is in fact unlocked! :roll: It will happily start with either CPH, and even if I unplug the transponder antenna on the ignition lock it still starts without complaint, not even a warning on the dashboard.
Maybe, maybe not as once the ECU/CPH has been unlocked by turning the key it stays unlocked for a fair old period of time, so before you get too excited try the new CPH in the morning and see what happens,,,,,
I did some more testing of this tonight.

With the new ECU it re-locks (and requires the transponder signal) after approximately 2-5 minutes of the key being off, or about 10-20 seconds after the alarm is armed.

The old ECU has been unplugged for well over 24 hours, I disconnected the transponder antenna to eliminate any chance of it picking up the key, swapped the old engine ECU back into the car (but left the new CPH) and it started first attempt.

Not only should it not start with no transponder signal, even with the correct key and transponder signal it should not start with a mismatched CPH ?

I then swapped the new ECU back in and it would not start without the transponder antenna being reconnected and the key held close.

So my original ECU is absolutely beyond doubt unlocked, which still begs the question, why did it get replaced and how long ago ?
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Post by addo »

...And what is it from?
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Mandrake
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Re:

Post by Mandrake »

addo wrote:...And what is it from?
Do you mean is it out of a Xantia or a 406 ?

Here's the old one:

Image

I haven't looked up the part number to see if it is the correct one (nor have I compared it to the part number on the new one to be honest) but I have no reason to suspect its the wrong model ECU.
Hell Razor5543
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Hell Razor5543 »

Apart from all the intermittent problems, that is. :-D :-D :-D
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Mandrake
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Mandrake »

Hell Razor5543 wrote:Apart from all the intermittent problems, that is. :-D :-D :-D
Yes but remember the car had no performance problems for the first 6 months I had it... As far as I know there are only two versions of the ES9J4 ECU - manual and automatic...

There are other rather different engines that use the same Bosch MP7.0 ECU hardware and look the same apart from part number, but with different programming/mapping that would not be compatible with this engine and would run very poorly if at all.

My main concern is why was the original replaced (did something in the car damage it, like a shorted coil) and if this one is unlocked it means that its almost certainly a second hand replacement from who knows where, and potentially not of the best quality.

For all we know maybe it was removed from a scrapped car that hadn't been running well, was unlocked and sold second hand without its full history being known. Anything is possible.
Hell Razor5543
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Hell Razor5543 »

I wonder if these might be worth a look;

http://www.ebay.co.uk/itm/CITROEN-XANTI ... 45fd61d91c" onclick="window.open(this.href);return false;

http://www.ebay.co.uk/itm/PEUGEOT-406-C ... 27d74d139e" onclick="window.open(this.href);return false;

EDIT; The first one matches for part numbers. Mind you, that is based on the part number of your ECU!

EDIT (again); Now we know there are (at least) two different ECUs for the V6 engine (for the Xantia and the 406), I would suggest you look up your VIN to see what ECU was originally fitted (but you probably are already doing so!).
Stempy
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Re: Xantia V6 broken exhaust (update: and rough low rpm runn

Post by Stempy »

Part no. for the manual box version is 0 261 204 410