About 2-3 a week my 1999 Mustang GT will stall while Im at a light. It cranks right back up. Right before this happens, the RPM's jump from 500-1200 a few times then it just dies. Do you'll think it is the idle air control valve? Something else?

 

Yes clean the IAC

 

Try cleaning the TB and IAC with throttle body cleaner. My wifes 00 GT had the same problem, once I cleaned them both the problem went away.

 

hmm that might be good information for my mom, her 94 mercury cougar(wit a v8 of course) has the same exact problem, i think i should tell her bout that