2003 Ford Taurus - Engine almost stalls in idle

A dirty IAC is a common problem causing this. Many times, it can be removed and cleaned to return it to normal operation. It may also require replacement if it is really bad and you have no patience to clean it. It will not always set a fault code in the system. Ford dealers and many well equipped independants have scanners that can test the function of the IAC along with the rest of the system. A new Ford IAC will set you back just under $100US for the part. Is usually easy to remove/replace. Most shops will charge an hour or so lable to run a diagnostic plus whatever time is allowed by the book to replace. At shop labor rates, cleaning is not usually cost effective. BTW, a complete diagnostic scan may uncover other irregularities that should be attended. Now, if you car has less than 50K miles on it, let the dealer take care of your problem under the emissions warranty. No muss, no fuss! BTW, the noise you hear is probably belt idlers and other things that normally make noise under these conditions. The a/c clutch is also probably going bonkers because of the erratic idle as it should.

Good luck Lugnut