I had the same problem. I performed the fix and it worked for 2 weeks, but I ended up replacing the IAC valve. Cost me $70, at the Ford dealer believe it or not!

Birthdate 1/6/2000 Mods: 35% Tint Bosal Exhaust K & N Air Intake, MAF Koni & Eibach Spec I/Spec Flywheel DMD http://www.villagephotos.com/pubbrowse.asp?selected=895138