I had an idling broblem for a long time before I figured out what it was. I ended up frying an O2 sensor bacause of a bad IAC solenoid. I had a bad IAC solenoid but replaced the O2 sensor first not knowing. The problem persisted and a month later replaced the IAC solenoid. Problem still persisted. After that I replaced practically everything that could be replaced. I later re installed my original 02 sensor (keept all used sensors) and the truck has run fine since. I believe that the O2 sensor failed due to the soot and unburned fuel going through the exhaust from running really rich. This was causing the truck to sputter and stall.

92 F150 XL 4x4, 5.0L AOD, Headers, K&N Air Filter, 3.55 Gears, LT235/75/15 Tires.