406 mad reving at idle (2200 - 2500 rpm)

My friend has a Peugeot 406 1.8 petrol 1996. At idle when the engine gets
warm after the cooling fan has cut in it starts reving on its own. The
reving is between 2200 and 2500 rpm approx and goes up and down about once
every second. The only way to stop it is to turn off the ignition. Does
anybody know what the problem is ? Thanks in advance. Steve.

 

One more thing to add. The engine autodiagnostic light does not stay on
when the engine is running. Steve.

 

I've seen this on my 406 1.8 16v a couple of times in 2 years.... I reckon
its some software instability in the controller causing the mixture to hunt
(or I suppose it could be a dirty connection somewhere on a sensor?). If you
turn off the ignition and restart the engine its fine. Perhaps one of the
guru's here will have a better handle on it?

 

John Ricketts wrote in message ...

Try cleaning/checking the idle valve as recently discussed in this NG.

Dont people read the posts here!

Bob