[Chadwick]

Clio 1.2 2004. 110000 miles.
After engine has been running for 5 minutes if return to neutral such as at junction then engine idles at about 2500 rpm.
Details: engine speed stays nearly at previous in gear speed and moves hesitatingly to this speed. Idling is ok on engine start and occassionally returns to 1200 rpm or even correct 800 rpm. Seems a bit hesitating accelerating and changing gear though could be just because trying to avoid this problem. If let idle a long time then speed can correct itself or even go up slightly to say 2800 rpm. Perhaps need to keep revs up when leaving neutral as can then stall and then be difficult to restart for say 2 mins.
Thanks

 

[SDN Motors]

If you come to a standstill and then blip the throttle, do the revs drop back down to normal?

Might be something simple like an EGR valve and/or throttle housing needing a cleanout.

 

[Chadwick]

Thanks for the reply. Blipping throttle does not seem to help. I have previously had problem with the throttle (housing was cleaned) but that is different. Does sound like something such as EGR. I feel engine management system has deliberately chosen to run faster. Does a petrol 1.2 have an EGR valve? (Presumably it has EGR but all Clio EGR valve references seem to point to 1.5 diesel.) I have an Elm 327 OBD II monitor but have not used it to monitor any analogue values (I'm not sure there any appropriate ones?) and there are no fault codes.

 

[Ralph]

Stick your scanner on and when your sure the engine is up to normal temp check the temp it should read about 90c if its a lot out suspect the temp sender the bigger of the two.

 

[SDN Motors]

Hmmm. Sounds like we would need a closer look. If you're ever passing Winchester, you're welcome to drop in. I'll stick the kettle on and ask Chris (resident genius and Bass Guitar player) to check it out.

 

[Chadwick]

It could as suggested be a problem with Coolant sensor. OBDII reports a few spurious isolated and long drops. Albeit the long drop is when engine was idling (and not very fast). See chart 400-575.

Here is a link to a zipped Excel spreadsheet of all available OBD II data including a chart. (Total time of chart is 50 mins.) It is less convincing as problem was not great this morning. Will probably choose to repeat.

http://www.dc101.webs.com/ClioElmCoolantDips.zip

 

[Ralph]

The thermostat could be playing silly buggers but they usually fail shut.
Have you checked any wiring round the sensor and the ECU, the cover can rub through the wiring nr the ECU.

 

[Chadwick]

Thanks for your help. Problem was fixed by replacing coolant sensor. (Could not even start engine when OBDII was reporting -10 C to -15 C. If leave for a few minutes temperature changes and can start. OBD II can nominally report down to -40 C.)