16v Idle Issue... High Rev... Slow Rev Down...

[Djmac]

Ive read about and noticed a few topics talking about idle issues, mainly issues with low idle and stalling!
mine is quite the opposite, with a real high idle sometimes reaching 2k, dipping then returning?
Theres also an issue with the return of revs, once the accelerator is depressed the revs take a while to return to its "idle", Ive checked the TB and the butterfly is working fine, no friction pausing the valve shutting!
Ive read it could be something to do with the temp sensor? Or the breather plumbing?
Just to note it has a KnN style filter (which i plan changing to stock)... When removing the breather part and covering the hose slightly the revs drop to a ideal idle, obviously if fully covered the car cuts out..
Any help would be great full, thanks alot! Dan

[spikenipple]

It's your Idle Stabilisation Valve, which is situated under the plastic cover at the front of the inlet manifold. The breather hose you are covering to alter the idle leads to it. Try taking it off and soaking it in petrol overnight, then giving it a good spray out with some WD40. Also make sure that the rubber bung that sits between the valve and the manifold is in good nick, if not then replace it as it may allow air through, causing a higher idle.

[Djmac]

Great response, thanks for the help, ive just put it in some petrol now to saok, the bung looks fine! ill have a test tomorrow and let you know, thanks again

[Djmac]

Just tried my friends idle control valve on my car and theres no difference Seems if i push down on top of the breather pip above the ICV it lowers the revs also? could it be an all out issue with the breather plumbing?
Does anyone have a 16v stock airbox going cheap?

[spikenipple]

Does the ISV click when you turn the ignition on? Check the voltage at the plug when the ignition is on.

[Djmac]

Ok, ive left it soaking over night, and just attached the plug to it and on turn of the key i can hear and have seen the internals working! ill plumb it in and see what the results are! Cheers

[Djmac]

Seems a little better but is still idling at 1500..?

[Metallix]

This also sounds like you have an air leak somewhere.
If this is so, ignore the airbox.  Air is getting into the intake manifold somewhere other than the throttle plate &/or ISV.

Check that all the little vacuum hoses are attached and that they are free from holes / tears.


Another one, is the idle switch working (the button on the throttle body that is pressed when the plate is closed).  Easy way to check is by trying your mates throttle body on your car.

[Djmac]

ok ive managed to get 100 of the idle, i removed the breather pipe under the ICV and it was slightly closed together, so i straightened it out, refited it and replaced the smaller pipe which leads to the inlet manifold!
i also tried bypassing the TB switch with a bit of wire, but made no difference to the idle!
Could it be anything to do with the MAF?
I also think the TB has been modified, like port and polished? Could this be letting air through making the engine work harder?

[Djmac]

Also just wondering if this is supposed to be connected? I dont have air con?