Idle not dropping off

[radzoule]

My car has developed a curious "fault" which feels like a management problem. When warm and coasting to a stop the idle generally won't drop below 1500 until the car has reached a standstill. When is does drop it does so very quickly, as if something has just been switched, rather than gradually settling down.

I fitted a new stepper motor about 6 months ago.

Anyone have any ideas as to what might be wrong? Throttle potentiometer? She's shunting a bit more than she used to and I understand this can sometimes point to that.

Any thoughts much appreciated.

PS re insurance, I just renewed and found that Tesco beat all the specialists even though their questions are less detailed (eg regarding whether you've owned one before, exactly how many years no claims etc).

[pullingpower]

I think they all do that.

[tahiti450]

AFAIK the ECU senses road speed through the speedo pick up circuit and this does indeed form part of the idle speed control. The idle speed therefore will only really settle when the car is at rest, and yes it does giver the impression of something being switched on/off as that is what is happening. I find this is what happens when if you drive off before the engine is warm and the ecu has finished the cold start cycle, in which case the idle speed remains "frozen" at "fast idle" through the stepper motor position, until you actually come to a complete halt at which point the engine speed drops back to the normal 800-900 rpm after a couple of seconds. Viola!

[s4s280]

RadZ, join my current thread hoo ha on "strangely" the same basic probs.

Thread is "P Poor flatting" - I've asked Steve Coule to join in on the thread with Pete/POD and a few others to nail this sucker once and for all.

Just going back to it now to post back my update, join me.

Bob