Help with surging idle

[95GTST]

Hey guys, recently had my FMIC fitted, and all seemed well, except for now... It's only been about a week since it's been installed, and I don't know if it's realated to the FMIC, but my idle is surging from 1200rpm to 2100rpm, surges about 3 times, then settles at 1200rpm. This happens anytime I put the clutch in, or car is in neutral (of course).

The car used to idle at 800rpm, after FMIC was fitted it was about the same. I've checked the throttle cable, it's as loose as it can go...

Any ideas before I take it back to the place where FMIC was fitted???

[Steve]

First thing I would be looking for is a vacuum leak - check all your pipes thoroughly.

It may not be on the cooler though (but this is most likely as those pipe joins have been messed with), so make sure you check every line/pipe/join/etc from the turbo outlet to the plenum, including AAC air line, BOV, boost guage etc.

[95GTST]

Thanks Steve, had a good look, can't see anything obvious. I'm taking it back there this afternoon.

[JimX]

If you can't find any leaks you could check the throttle position sensor. Also there is an idle screw adjustment in the back of the plenum which might need adjusting.

[95GTST]

Yeah Jim, I tried adjusting it and it sort of went down a bit, but not much... I ended up leaving the car with them and they fixed it, problem was that the ignition timing valve (I hope it's right) was full of carbon and crap. They cleaned it out, give it a good lube and she's all good now

[GunMetalR33]

This might sound stupid but where is the ignition timing valve?

[blind_elk]

I think he's means the AAC (Auxilliary Air Control) valve - sits on the back of the plenum chamber.