My son's 2000 Ford GT 4.6l has a issue....It starts fine, but once in while, it will not idle at start up. You have to tach at about 1500 for a few minutes, and then get on the road fast. After about 5 min of driving, it idles fine.....what gives? Oh, and this dosnt happen every time, just once out of every ten times...

Its hard to tell without me being able to see a scanner installed, but it seems as if the IAC valve may be sticking, but then again ive seen these same engines have a bad coil pack and do the same. I recomend taking the IAC (idle air control) valve off it and cleaning it and the chamber where it mounts, possible use some carb cleaner and some copmressed air, but watch out for the mass sensor as high pressure will damage its sensor. also clean out the throttle body where the fly closes in it.