Quote Originally Posted by JohnL View Post
OK, so disconnecting the IACV connector doesn't stop it happening, though it does make some change. Whether the IACV is faulty - or is perfect but being 'told' to do the wrong thing at the wrong time, to make sure that the 'leak' isn't happening through the IACV (whether the IACV is faulty or not), try fitting a 'blind' gasket at the IACV / plenum faces.

Making such a gasket is dead easy, take the IACV completely off the motor and make a paper gasket using light cardboard (or prefferably proper gasket paper) that will block the inlet and outlet ports in the IACV. The only holes in the 'blind' gasket will be the two bolt holes, so no air can pass into or out of it. Refit and start up.

If the fast idle problem goes away then the problem must at least be associated with the IACV, but may or may not be the IACV itself. At this point you would need to swap the existing IACV for a known good unit (without the blind gasket), just to see if changing it fixes the problem. If it does then your IACV must be faulty, but if it doesn't then your IACV is probably OK but being 'told' the wrong thing by the ECU, which itself may be being told the wrong thing by some sensor....

If fitting a known good IACV doesn't fix it you might be looking at the ECU, but more likely one of the sensors informing the ECU. This still doesn't conclusively mean there might be no other point at which a leak might exist, possibly a leak inside some sensor on the engine side of the butterfly(?).

You can drive the car with the IACV disabled in this way (with blind gasket fitted), but idle will probably be low and definitely low when you use air-con or other auxilliary loads are on the engine. You'll also probably find you have some drivetrain 'snatch' that wasn't there before, which is a bit of a pain but doesn't really hurt anything.
JohnL thanks for your reply, I think im on the same steps as you. i didnt actually make a gasket but i thought if there may be a leak in the IACV then i probably should ensure that its not there. soo i used some silicone gasket maker. Put that on and waited bout 5-10 before i started the car. the gasket GOO has worked for me before in similar situtions so that would be the same effect as your Motor cardboard idea (but yeh i know what u meen by the cardboard, used that stuff before).

But i think yeh it must be something with the IACV...thats really the only thing changing when i plug and unplug the Sensor from it. Going to take it to my uncles (mechanic) tomorrow and ill pick up another IACV from a wrecker on the way and give that to him.