Idle problems

[jimmyV8]

My 98 Chimeara 400 wont settle to an idle once throttle released. The is a delay of 5-10seconds while the revs stay at around 1500-1800revs before dropping to just below 1000. On start up same thing happens. Its starting to get on my nerves as when I lift off the throttle it is still trying to pull and in 5th gear 1500 revs is about 40 MPH which the brakes are sometimes working hard against. I have tried the usual stepper motor but is clean and had car looked at by a specialist who says its just how my car is, except it never used to be like this!

Any suggestions would be much appreciated, sorry if my message isnt too clear!! Cheers

[V8 Animal]

who says its just how my car is:laugh
Sounds like sticking throttle cable.
V8 Animal

[blitzracing]

The idle control system needs everything to be in prefect balance to function properly. Things like over rich mixture (Fuel pressure), failed sensors, air leaks or obviously sticky stepper motor can lead to such behavior. Ive covered in in some depth here:

http://www.g33.co.uk/fuel_injection.htm

If you can borrow a fault code reader it may show something up, if the ecu is in fall back mode. I think one reason for the high RPM is a fail safe system to help preserve the catalyst if the fueling is wrong, but I cant prove this one. The "specialist" is talking rubbish !!

Mark

[jimmyV8]

Well I have unpluged the ECU and connected it again and car is running totally normally again. Obviously I would like to know what caused it to run differently but for now will have to see how i get on. Thanks.