My XM (2 litre turbo Automatic, 1995 Mark 2) is pinking, but not seriously.
Enough to be noticed though.
I have changed the spark plugs and air filter and gone through the basics, but it still pinks.
Eventually I took it to a Citroen specialist.
No error codes came up on their diagnostic computer.
However, they have traced a fault to the throttle potentiometer and have advised me to change it.
They believe this is the likely cause of the pre-ignition problem.
What do you think?
All advice welcomed.
Thank you.
AndUK
XM Pinking - Any ideas please?
Moderator: RichardW
The throttle potientiometer directly reads off the position of the throttle flap.
If for any reason the potientiometer signals a faulty position back to the ECU - you could then get a lean running engine which is known to cause pinking.
The theory fits - if a fault in the potientiometer causes a constant position signal offset.
As long as the position signal is sensible - i.e. within the normal operating range - the ECU will not take it as a faulty signal - but simply do it's job based on the actual signal received - hence no fault codes.
The throttle potientiometer is a known bugger on modern cars - and the common cause to strange engine rev's. Only if it's worn to such a stage that the signal is completely lost at certain throttle positions - you get an ECU stored fault code. But then the fault code stored most likely refers to a Lambda problem - since the gas mixture get's insane - and likewise the Lambda value.
If for any reason the potientiometer signals a faulty position back to the ECU - you could then get a lean running engine which is known to cause pinking.
The theory fits - if a fault in the potientiometer causes a constant position signal offset.
As long as the position signal is sensible - i.e. within the normal operating range - the ECU will not take it as a faulty signal - but simply do it's job based on the actual signal received - hence no fault codes.
The throttle potientiometer is a known bugger on modern cars - and the common cause to strange engine rev's. Only if it's worn to such a stage that the signal is completely lost at certain throttle positions - you get an ECU stored fault code. But then the fault code stored most likely refers to a Lambda problem - since the gas mixture get's insane - and likewise the Lambda value.