'04 Cobra cold-stall problem

dunno? Im a noob, but theses types of post someone always says check the IAC or clean it

It's problem with the factory tune. It's known as... "The Stall!" There's an SSM from Ford and the fix can be covered under warranty. There's a newer ECM calibration that will help correct that problem. I have a copy of the one for the 03 and I believe there was a later one for the 04's.

16293 2003 MUSTANG COBRA - STALL ON DECEL
SOME 2003 MUSTANG COBRA VEHICLES MAY EXHIBIT AN ENGINE QUIT CONDITION ON DECELERATION. THE ENGINE WILL RESTART IMMEDIATELY. THIS MAY BE CAUSED BY THE CALIBRATION OF THE POWERTRAIN CONTROL MODULE (PCM). TO SERVICE, VERIFY CONDITION & REPROGRAM THE PCM WITH THE LATEST CALIBRATION AVAILABLE VIA THE JUST IN TIME PROCESS IF YOUR WDS COMMUNICATES WITH FORDSTAR. CALIBRATIONS ARE ALSO AVAILABLE ON THE PROFESSIONAL TECHNICIAN SOCIETY (PTS) WEBSITE - SELECT 'WDS' THEN 'PCM REPROGRAMMING' AND CLICK 'INSTRUCTIONS' FOR DOWNLOADING. THE CALIBRATIONS WILL ALSO BE AVAILABLE ON WDS RELEASE B21.3.

Or... you can have it fixed with a custom tune from any of the reputable tuners out there.

U.M.