Citroen XM Forum

Greetings from the Netherlands everyone!

My name is Phil and I was wondering if anyone has experienced the following aswel.

My xm with the manual prv v6 drives very nicely, gives power when you need it and runs great stationairy, however only when letting go fully of the gas pedal and when giving gas again from closed throttle, it jerks slightly after half a second. You could be redlining the car and letting the pedal go untill the last mm and everything runs smoothly, but if you let it go all the way then it jerks. Working the pedal very softly and smooth does not change this.

Things that already have been changed:
Lamda sensor
Spark plugs
Knock sensors
Clutch


What could cause this and where should I look?

Kind regards!

It would be worth investigating the overrun fuel cutoff, and in particular make sure that the ECU is the correct type for manual transmission and that the throttle potentiometer is adjusted correctly.

Start by cleaning out the idle air control valve and throttle flap and housing, check the throttle just goes completely closed at idle and check the throttle potentiometer is reading 0.5v Dc at throttle closed and over 4.5v Dc at WOT.

Check the TPS voltage is sound at the Ecu connector, I think should be pins 11-34 and 33-34 respectively.

Engine management information can be found in this linked to thread viewtopic.php?f=13&t=10588

Thanks for the replies! I shall be checking this weekend and will post an update

Also, ensure there are no air leaks into the intake manifold and that all small bore vacuum pipes are clear.
A quick check is to crimp the Idle Bypass feed hose at which point the engine should stall, or run slowly, below 500 Rpm.

A smoke test should be conclusive for air leaks.

Hello again, I had some trouble locating the TPS. Does anyone have an online repair manual for the xm? Or should a I find a second hand haynes. Thank you!

Also, I crimped the bypass feed hose, when just squeezing it by hand it idled lower but there was a whistling noice, when actually folding it on itself and closing it off it idled very low to the point of stalling.

The Throttle Position Sensor (TPS) is mounted on the rear end of the throttle spindle.

If the engine nearly stalled on blocking the idle bypass hose, it appears there are no vacuum leaks.

Have you downloaded and read the information from the previously linked to thread. The Fenix3 information has the detail you need.