The late 80s forum and the 302 forum can both give you the proper information. Usually cleaning the IAC helps, that's why I recommended it, but go to one of those forums for more info.
87-96 forum:
1987 - 1996 F150 And Larger F-Series Trucks - Ford Truck Enthusiasts Forums
Small block forum:
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W) - Ford Truck Enthusiasts Forums