Been trying to track down the reason for a code 172 (lean) for a while now. The other day i removed and cleaned my IAC valve. when i put it back i cleared the memory started up and the idle was real low and unpluging the IAC made no difference. Went and got a new IAC and installed, now idle is 1200-2k. The voltage at the IAC is 10.56 KOEO and 14.5v running. disconecting makes no difference. i checked the TPS 0.89v idle and 4.5 WOT. Ran KOEO 111 Ran KOER 411 412 unable to control engine RPM. but atleast my 172 code is gone... checked for vac leaks

any ideas

 

Did you read these?
https://www.f150online.com/forums/se...archid=4164358

Did you buy the cheapest IAC from the zone, or did you get a Wells with a MotorCraft PN from Advance?

 

yes i did a search and yes i got it from advance

 

problem solved. Returned the valve to advance and exchanged and bingo. Now 700 rpm