Help small running fault.

[DAVIDP20V]

This morning and for the last few, when driving to work i have noticed the engine revs being very ir-r-r-atic as it slowly warms up. [img]images/graemlins/nodder.gif[/img] it revs up and down around 1000 rpm.
By the time i have done a few miles and got to my 1st set of traffic lights the revs drop right down (virtually cutting out!) and the car revs higher to stop it cutting out !!! [img]images/graemlins/033102bad_1_prv.gif[/img]
As i drive i come to the junction for my work, slow down and stop waiting for the traffic to clear and the car cuts out, so i have to restart, which it does instantly and the fault is gone ! [img]images/graemlins/clap.gif[/img]

now to get it home without the running fault i have to start the car let it idle for a sec, switch it off and re-start and the problem wont even show itself. what a wierdo! [img]images/graemlins/24430-audibash.gif[/img]

whats going on any ideas, much appreciated [img]images/graemlins/thumbs.gif[/img]

[jubjub]

I had something very similar on mine, it used to hunt on idle,200rpm-1000rpm,and on two occasions cut out completly, once coming of a slip on the A2 [img]images/graemlins/shocked.gif[/img]Sorted at Quatrosports,the culprit being an "idle control valve" i recall.

[scillyisles]

Yep it's the idle control valve.

[DAVIDP20V]

Was it cleaned or replaced ? my chaps [img]images/graemlins/thumbs.gif[/img]

[jubjub]

I believe Kim put a new one on,the part was about £30 but don't quote me on that....

[DAVIDP20V]

you are a star, cheers matey [img]images/graemlins/clap.gif[/img]


i will have a play tmrw morning
[img]images/graemlins/thumbs.gif[/img]

[Jani]

Another thing to check is the throttle damper setup, it is at the throttle body (the thing that slows the return of the throttle).

Engine turned off, open hood, play with the throttle, and make sure you eventually hear a click everytime the throttle comes to rest. That is the idle micro connector, it won't go to idle mode unless it gets contact-causes erratic idle or stall.

If the car is stalling when you press clutch at low revs (stop at lights etc), then increase damping (you need some tools, 13mm wrench IIRC) by making the damper longer, just make sure it still clicks everytime.

If this doesn't help, then it is the ISV (idle stabilezer valve) that's sticky. Change it, or clean it inside with solvent, and by clicking it back and forth with external 12v voltage.

Another thing to check while you are playing with the throttle body, is to make sure it opens fully when pedal is in the floor. You need 2 people to do this, one pressing throttle pedal, other checking under the hood that it really opens fully. If it only opens 90%, then Motronic will never give you full boost and mapping, and throttle body will disturb the airflow as well.