Citroen XM Forum

Many thanks Will and the Company appears to be in Poland! With regards, Matthew T.

czechoslovakia I think, not that it will matter

The car is certainly testing you!

Yes Dave that is definitely true, but when it goes well it is a dream! I have now put 300 miles on the car since returning to the road and weirdly the restricted revving does seem to be curing itself, or at least when it does occur it is nearer 4,000rpm and therefore not so noticeable. Here is a recording made before the improvement and please note that at the higher revs my foot was hard on the floor. Regards, Matthew T.

Unfortunately I cannot post up the video, I am guessing because the file is too big!! Regards, Mathew T.

I obviously spoke to soon as the restricted revving problem has not quite gone away although I have managed to upload a video on u tube: https://www.youtube.com/watch?v=CW2kDzgs_G0" onclick="window.open(this.href);return false;

As you will note on this occasion the engine did run up to nearly 4,000rpm, which was better than before, although my foot was hard on the floor! The tick-over is fairly smooth and just where it needs to be just under 1,000rpm.

Earlier today I also tried other plug leads so here is a complete list of the items changed:

plugs and leads
injectors
sensors to crankshaft, map, temperature, manifold, throttle, oxygen etc.
idle valve
alternator
ecu
fuel filter
fuel pump
pulsation damper and pressure regulator
ignition coil and module
distributor cap and rotor arm

Any further thoughts or suggestions would be most welcome.

With regards,

Matthew T.

I dont like the look of that or the way the Tach moves, at best i would think its ignition related, like its hitting the elctronic rev limiter (does it even have one?) what does it do on the road? any lack of power while driving? what happens if you roll onto the throttle gently?.

D

Thanks Dean and I am not sure if the 12v has a rev limiter, although the 24v certainly does at around 6,400rpm, as I have experienced! With the 24v at peek revs the effect is certainly quite similar with the missing etc. The tick-over at present is perhaps a little bit lumpy but basically the engine 'pulls like a train' with no shortage of power or acceleration up to around 3,500rpm. A gentle application of throttle has the same effect really, ie. the engine will just not go any faster! It is strange that the car seemed to running almost normally a couple of days ago, but perhaps the problem just moved up to higher revs ? Regards, Matthew T.

If the 24v does then i would think the 12v would too but im not sure what sort of fault would trigger that at 4k rpm, the way the tach jerks about suggests (to me at least) there is an electrical problem there with the ignition but i cant think what it could be, sorry Matthew. Have you checked live data on a lexia to see if anything odd is happening with ignition timing etc?

D

That is helpful Dean and I am sure you are right about the 12v having a rev limiter. From the limited research that I have done in the subject, rev limiters work through cutting off fuel, which is rather what it feels like in this case. Apparently in cars of this era at least the ecu sends a signal to the fuel pump relay to switch off, so I could try bypassing the relay I guess? I have also just swapped the relays from another car, but that brought no improvement. My other plan is to further check connections under the lhm tank, as I remember having an earlier problem with a broken wire in that location that resulted in no fuel supply! Regards, Matthew T.