High Idle Problems

[Monkey276]

I have a 4L HC engine. The car takes nearly a minute to return to idle. It holds at 2000+ revs and slowly decreases. Problem seems worse when hot.

[tvrbob]

Sounds like the stepper motor is slow to react. It's worth taking it out and cleaning the plug and seat.

[GreenV8S]

First of all get it idling nicely and then unplug the stepper motor. If the problem immediately goes away you know it is caused by the stepper motor. Cleaning the stepper motor would be the first thing to try. If the problem continues with the stepper disconnected then you probably have an air leak in the intake, or one of the vacuum hoses, or the brake servo.

[steve-v8s]

Out of interest has your engine or ECU been fiddled with by one of the “ tuners” or is it standard.

[tahiti450]

All as above but also: If youve got PAS check the large bolt that secures the reservoir bracket to the plenum base. The tapping for this goes straight into the plenum chamber and if the bolt is loose extra air will be able enter the induction system this way and raise the idle (and weaken mixture, notwithstanding lambda correction).