Idle/tick Over Too Fast

[vic]

my 1997 1.8 injection xantier tick over speed is ok when the engine is cold but as soon as the engine warms up to normal engine running temperature the tick over ranges from 1250 to 1750 rpm, the local citroen garage told me it was the stepper motor so i bought a new one from them (£111 plus £43 diagnostics charge) and fitted it but it has made no difference, solent citroen now tell me it needs to go on the mapping machine again. i feel that just maybe they r taking the proverbial, can anyone tell me whats wrong as she drives normally just the revs are wacky in idle

[Guest Colin Hunter]

Don't know much about current petrol injection systems. My last petrol car was a 2.0 MG Montego! (F Reg!) There was a procedure to set the base idle speed on that system (Lucas EFi) which entailed setting the throttle position with a 1.5 thou feeler gauge between the butterfly and the body, and starting the engine with the idle control stepper motor unplugged. (Engine at operating temp). If the car wouldn't idle very well the base idle speed was then set by using a bleed screw on the throttle body. When the idle speed was at the correct value the stepper motor was plugged in. The system would then take over and the idle speed was controlled by the stepper motor which would open when the engine was cold or when put under load at idle (Power steering or trickling in traffic etc.) and prevent the engine from stalling.

 

As I say that was a few years ago and the systems are more advanced now but I imagine the principle is similar. Have look at your throttle body to see if there is a bleed screw on it. It may well be done by setting the stop or base position of the thottle butterfly itself. If the throttle stop screw is holding the butterfly too far open or the bleed screw is too far open the car will be OK when cold but will race when hot and the stepper motor will be defeated and will remain shut and unable to control the idle speed.

 

Cheers. Hope this helps. :)

[vic]

my 1997 1.8 injection xantier tick over speed is ok when the engine is cold but as soon as the engine warms up to normal engine running temperature the tick over ranges from 1250 to 1750 rpm, the local citroen garage told me it was the stepper motor so i bought a new one from them (£111 plus £43 diagnostics charge) and fitted it but it has made no difference, solent citroen now tell me it needs to go on the mapping machine again. i feel that just maybe they r taking the proverbial, can anyone tell me whats wrong as she drives normally just the revs are wacky in idle

 

thanks for the sugestions about the screw for adjustments ive had a look and unfortunatley nothing, also the butterfly has no adjustments on it either so im stumped there 2, ive unplugged the stepper motor with the engin running and that made absolutly no difference what so ever then i plugged the stepper motor back in and that did nothing, im begining to think that solent citroen sold me a duff unit and just want to get my car in so that they can charge me another £43 and tell me its another sensor that will probably cost me in excess of another hundred pounds plus, any other sugestions or help would be greatly apreciated

[Guest Colin Hunter]

thanks for the sugestions about the screw for adjustments ive had a look and unfortunatley nothing, also the butterfly has no adjustments on it either so im stumped there 2, ive unplugged the stepper motor with the engin running and that made absolutly no difference what so ever then i plugged the stepper motor back in and that did nothing, im begining to think that solent citroen sold me a duff unit and just want to get my car in so that they can charge me another £43 and tell me its another sensor that will probably cost me in excess of another hundred pounds plus, any other sugestions or help would be greatly apreciated

 

Sounds as though air is getting in somewhere it shouldn't and causing your high/intermitent idle speed. Check for splits in the air intake trunking (unlikely to cause this symptom) or between the throttle body and manifold. Are there any blanking plugs in the manifold which would normally supply vaccuum to the brake servo in another application? Spraying some WD 40 or similar around this area, the butterfly spindle could be another source if it's worn, will cause the engine to stutter or perhaps race if it gets drawn in with any air ingress. The stepper motor is supposed to control idle speed by opening if the engine speed falls too low. It would appear that the engine is getting it's air from elsewhere! An independant Fuel injection specialist may be a better bet.

 

Cheers again. Sorry my first suggestion was off mark. As I say, It's a while since I dealt with a petrol injection system. :)

[Guest Colin Hunter]

Just had another thought regarding the source of the "Extra air" if that's what it is. Is the throttle butterfly held onto the spindle with two screws? I recall reading somewhere that someone had a similar problem and that one of the screws had fallen out and had vanished into the engine! The engine was pulling enough extra air therough the screw hole! You could maybe take off the air duct and have a look!

 

Cheers. Unlikely but possible!

[vic]

Just had another thought regarding the source of the "Extra air" if that's what it is. Is the throttle butterfly held onto the spindle with two screws? I recall reading somewhere that someone had a similar problem and that one of the screws had fallen out and had vanished into the engine! The engine was pulling enough extra air therough the screw hole! You could maybe take off the air duct and have a look!

 

Cheers. Unlikely but possible!

 

thanks for all of the help but unfortunatley nothing has helped, i took the car back to solent citroen and they say they dont kno whats going on and it will need several hours of investigation because the computer analyser isnt showing any faults so it seems that the people at solent arent as good as they think they are, one thing that strikes me as a bit of an odd thing is that the revs only increase when the water temp goes to the 80 deg mark on the guage. any more helpfull sugestions greatly apreciated thanks Vic