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

[Mandrake]

Just doing a bit of reading on MAP sensors and then found myself reading about EGR valves, could a faulty pipe on the EGR valve cause similar symptoms ? According to what I was reading EGR valves usually disable recirculation of exhaust at idle and also under wide throttle conditions, to avoid rough erratic running, if the pipe from the exhaust to the EGR valve had fallen off then when the valve activated it would be feeding extra air in causing a lean mixture instead of inert exhaust gas ?

The idle is fine and the wide throttle performance seems ok, so this seems to fit the symptoms somewhat, as it would cause lean rough running (and possible missing) with a light throttle but not while idling. Next question is where is the EGR valve on the V6 so I can check it

Unplugging the connector to the EGR valve might be a quick way to test this theory ? (Although that may also trigger an engine management fault warning ?)

[addo]

Lexia will show you MAP readings, also injector dwell and coil charge times (the clue to a dead coil). It may reveal the sensor reference voltages, too - not sure on a Xantia.

To manually test a coil you'll need it removed; identify the common positive feed to all three and then the relevant negative trigger. While a 12V square wave would be ideal, manually flicking the negative on and off rapidly should induce a fat spark in a grounded plug.

WOT performance is best assessed under heavy load. That's when you'll see just how the catalytic is coping, all alimentation sources and the cooling system. Just pedalling it hard won't reveal as much.

[xantia_v6]

Next question is where is the EGR valve on the V6 so I can check it

The es9j4 does not have EGR.

[Mandrake]

Next question is where is the EGR valve on the V6 so I can check it

The es9j4 does not have EGR.

Well I guess that rules that out then

I thought EGR systems were pretty much mandatory these days ?

Looks like I'm back to the MAP sensor as the prime culprit. Can they be cleaned and checked, or if the electrical connection is ok is it just a matter of substitution with a know good one ?

I noticed while driving today under light throttle up a hill it was feeling a bit hesitant and erratic, with small surges of extra power, as if I was actually modulating the throttle, that would be consistent with a flaky MAP sensor ?

I have the day off today waiting for the boiler repair man, I would have a look under the bonnet to see if I can find where it is if only it wasn't blowing a gale and pouring down...

[Mandrake]

Found the MAP sensor, easy once you know what it looks like... cleaned the connector, no change.

This problem seems to be getting worse by the day, overall power is down a lot, no zip to the car at all, and its really struggling between 1000-2000rpm, shuddering, stuttering, surging, making that strange vibration/grinding noise (which I presume is something in the engine bay rattling due to excessive engine vibration under low rpm load) so I'm now leaning strongly towards misfiring.

I think it's now got to the point where I need to pretty soon find a Lexia owner within driving distance to run a diagnostic, or take it into the local stealer (1 mile down the road) to run a diagnostic.

I'm guessing that coil packs on the V6 are an expensive item if it turns out to be that ? And presumably one or more plugs will now be badly fouled if that's what the problem is...

[RichardW]

David Hallworth (DHallworth) has got one, and is just out past Paisley somewhere. I think xantiacolin is near Falkirk and has got one too, but he hasn't posted much lately. Failing that, there is camautos in Rutherglen who are French specialist, probaly got one, or Graeme Harper's outfit off Argyle Street in Glasgow.

Either that or buy one - not that much more than a diag session if you've got an XP laptop you can run it on!

[Mandrake]

When you say not much more than a diagnostics session (I assume you mean at a stealer) that's either a very cheap Lexia or an expensive diagnostics session ?

I'm already on the waiting list for the Lexia group buy (I like to be as self sufficient as possible) but no idea when the next one will be. If you're referring to getting one from EBay I'm quite wary after reading tales of woe from others that have tried this, given that there's quite a few different clones around and not all are created equal.

I might give David a PM and see what he says. I'm working silly shifts at the moment so it would be a week or so before I could get a chance to do anything about it anyway. Hopefully it doesn't conk out completely in the meantime!

[magictorch]

I have used these before:
http://shop.prolux-systemtechnik.com/en ... insert.htm" onclick="window.open(this.href);return false;

I have also seen another one similar in the trade magazines that is designed to connect to cat convertors. Hope this helps. I am interested as I picked up my V6 Exclusive yesterday.


I have never had so much fun

[Mandrake]

I have used these before:
http://shop.prolux-systemtechnik.com/en ... insert.htm" onclick="window.open(this.href);return false;

I have also seen another one similar in the trade magazines that is designed to connect to cat convertors. Hope this helps.

Thanks for that. My bodge actually seems to be holding up well so far, no gas leaks or problems

I am interested as I picked up my V6 Exclusive yesterday.


I have never had so much fun

Are you alluding to the performance of the V6, or the "fun" of fixing a myriad of small problems in a 10-14 year old Citroen ?

[myglaren]

The group buy has changed, see Richard's recent posts in that thread.

[magictorch]

I was aluding to the recent purchase !

[Mandrake]

Ok, calling all V6 experts.

I now have a Lexia and have successfully run a diagnostic. Initially I was disappointed that it reported no faults recorded for the engine ECU, however on looking at the live sensor data I think it confirms that there is a problem with one of the coil packs, so I'd like someone with a bit more experience to have a look at the sensor data to confirm my suspicions...

Below is all the sensor data while the engine was idling and warmed up: (some scrolling may be required!)

(continued in next post)

[Mandrake]

I also repeated the ignition section at 2000rpm:

Of particular interest are the Coil 1/5 readings. I don't know exactly what the measurement is measuring but I'm pretty certain that Coil 1/5 shouldn't be close to zero all the time while the other two coil group figures fluctuate slightly but stay around the same as each other.

I'm assuming then that I have a faulty Coil 1/5 bank. If that's the case, where do I go from here ? Is that one of the back hard to get to banks or one at the front ? Expensive ? Hard to replace ? Etc. Does one coil run a pair of cylinders, so does a faulty coil mean that I'm running on 4 cylinders instead of 6 most of the time ?

One other suspicious reading is the Air Temp R and Air Temp S figures - which if I remember correctly were reading somewhere around 45 degrees with a cold engine on a cold Scottish night They didn't change reading much when the engine warmed up either. Is this a sensor measuring the air temperature of the air intake to help calculate the intake charge density ? If that sensor is telling the ECU that the ambient air is always hot then no doubt that is going to upset optimal running a bit too...

Looking forward to any comments/suggestions on where to next.

[Mandrake]

One other thing, while I was going through the various diagnostics my heart skipped a beat when it reported stored faults for the gearbox.

Both are intermittent and one looks fairly benign:

Which I assume is a slightly dodgy electrical connection to a speed sensor (where ?) - its only been recorded once, however I have sometimes noticed weird shifting behaviour where for example I'll be going up a hill with a moderate throttle, it will change up from 2nd to 3rd and then change back down to 2nd again only a second later and then a few seconds later go back up to 3rd again - all with a constant throttle and a gradually increasing speed. I had previously suspected that the gearbox may not have been reading the road/engine speed reliably on occasion, perhaps this confirms it.

The second intermittent fault looks a wee bit more ominous, has been logged 5 times, and I'm not sure what it's trying to tell me:

Any thoughts on this one ?

[CitroJim]

It's too late and my brain is calling time on me for the day Simon. I'll give my thoughts tomorrow morning if the old brain allows...