IAC idle problem....need help FAST!!!!!

I'm on my second '99 GT which had this problem. The Ford shop manual indicates that the IAC SHOULD NOT be cleaned as it is coated with a special sludge. As you discovered, cleaning it doesn't work or only works temporarily. You have to replace the IAC. It may be cheaper from an auto parts place (~$50) than from the dealer(~$80).

Btw, after searching for an answer to this problem on this and other mustang boards when I first experienced it I learned that this is a very common problem with the late-model GT's. This IAC problem really ought to have been properly addressed by Ford. I filed an official complaint with the NHTSA but never heard anything back from them.

there have been tons of threads about this. yeah just replace the iac. i had that prob on my 98 gt and once the car would warm up it'd be okay, but def had to keep my foot on the gas for the first couple minutes.

Sometimes you can remove the IAC and clean it but it is just a temporary fix. Had to bite the bullet and buy another one from FORD. Call around though. 4 dealerships only 30 miles apart had price differences of $35.