My Citroen XM 3.0 PR-Vestige

[russ92xmsed]

That's very good if its bettering the 2.0, albeit by a smidge.

[misha]

It will consume less fuel on open road than 2.0i because the engine is stronger and it will run on lower rpm than 2.0i on the same speed.
City stop & go driving would be around 15-20l/100km.

[Dieselman]

Having to stretch the V belt on is normal with diesels, so I'm not surprised yours is that tight.

[Dean]

I didn't realise the Diesels were the same Will, There was never a problem with the 2.0 engine but it had miles of travel on the hydraulic pump where the V6 doesn't so the belt almost has to be too small to not run out of travel when it beds in.

I have to look into the hesitation now, at the weekend it was hardly noticeable but this afternoon it was pretty constant above 2200rpm and with more than slight acceleration, normal driving doesn't take it above this threshold but when having a little fun it was holding back all the way and at one point wouldn't accelerate any more until i eased off the throttle so the box changed up to drop the revs. With the problem coming and going it will be tricky to trace but i may try fitting my old coil and see if that does anything.

Tested the spare fuel pressure reg and fitted it to the car, swapped the MAP sensor too even though the lexia live data seemed to show the other one was happy.
If its missing it's doing it on multiple cylinders but it feels more like strong hesitation and when it does it the exhaust produces muffled pops so i am suspecting an ignition fault and the pop is unburnt fuel in the exhaust.

D

[White Exec]

A plug or lead misbehaving? IIRC doesn't this show up as hesistation more noticeable as throttle is opened wider? You're right - weak mixture would not produce popping in the exhaust, although wandering timing could.
I have cobwebs on this - it's been a long time...

[Dean]

You seem to be going in the same direction as me Chris, the valve timing is correct now!, i've no idea what the ignition timing is doing and tbh I've not had reason to check on any vehicle I have owned so I don't own a timing light.

I put the old Coil back on last night and it runs much better but still hesitates a bit above 3000 rpm now, so changing the coil has improved but not cured the situation, I don't think for one minute the coil is the issue, it must be something I disturbed..............

I would say that the hesitation is above 2200rpm (as I don't know if this latest improvement is just coincidence and it's just having one of it's good spells) and the more throttle (load) is applied the worse it gets, sometimes it pulls through it and cleans up at around 4500rpm and sometimes it wont.

If the leads or leaking electricity it will be in the plug wells but they are all well insulated there with big rubber boots and there is no physical damage to them.
I really need to check my new plugs and see how they look.

D

[Dean]

I have had a chance to look at this today.
The long and short of it is that the plugs look OK to me, nothing horrific and the ground strap of the plug has the heat line in about the right place
plugs by Deanxm, on Flickr
plugs 2 by Deanxm, on Flickr
It kind of feels like the timing is drifting out so for starters I looked at the front knock sensor, my poor memory meant I had forgotten about having no power to the front knock sensor and ICV. I have ICV power now but no reference voltage to the front know sensor, rear sensor has 5v exactly on pin 2.

I think I have found the issue, why does the front sensor have no voltage at pin 2? when I get home tonight I will open that section of loom up and investigate, see if I can find where it is going.

D

[Dean]

Broken again!
IMG_3382 by Deanxm, on Flickr
I traced the fault back and found that pin 2 from the front knock sensor has perfect continuity with pin 31 on the ECU, i can only assume the problem is the ECU not outputting a 5v reference voltage. I have covered a few miles now and so hooked the Lexia up to find no faults recorded, the trouble i have is that every 6 seconds the ecu removes the faults from its memory as well, when it does this the lexia screen flickers.
With the ignition turned on the EML flickers every 6 or so seconds too and I'm not sure this is correct either.

Time to pull the ECU out and hunt down an alternative i guess.............. a spare would be useful for the future and with everything else working except this sensor and the random hesitation which today turned into what felt like someone turning the ignition on and off very quickly im not sure what else it could be.

D

[citroenxm]

Fenfix 3 ecus dean?? I think i might have some.. no good to me now.. ill have a look im hoping to get to the farm this week..

[Dean]

Thats very kind to offer Paul and i may well want one if you have an early auto type.
I have opened up the ECU and there are the small components, very tiny and square which are in different colours (no idea what it is yet), this has 5.3 V going to it fed on a common 5v track ,on the other side i only have 1.75v, this track then goes into a resistor which is outputting 0v, this then goes straight to Pin 31.

I think i can also see 4 tracks somewhere else on the board that have been scratched through but i will need to break out a magnifying glass as they are super tiny, im not sure if they have been wiped out completely but there is a mark across them.

I will see if i can get a photo.

D