I have a 1993 Ford F150. I just recently put a new true dual exhaust on it. This may or may not have anything to do with my problem. When idleing my truck's rpm's go up and down and sometimes will even stall. I replaced the O2 sensor, but have been told the it could be an IAC valve/motor, amoung many other things. It has an automatic trans. has anybody had this problem or do you know a solution???

 

Did you install cats or not? It may be flowin to freely, and the computer could be going nuts.

 

Yes I didn install two cats. I figured probably the computer.

 

Id test the TPS, and check the operation of the IAC.