i have a 1997 f-150 4.2l v6, and after the last oil change the idle is all messed up, at one point when i let off it will idle around 1300, then come down and be fine, then the next with will idle around 500-600 and want to die any ideas?? it also seems worse since it got really cold??

 

Sounds like the IAC motor. Mine acts up couple times a year, only when cold. Sounds like a classic case. May also be a vacum leak, a small crack in a hose contracts in the bitter cold. You'll find out next week if we get that -20 below stuff they are talking about here in Minnesota. Any vacum lines in the vicinity of where you work to change oil?


Spotty

 

no lines around the filter or oil pan, whats the iac motor??

 

The IAC motor is short for Idle Air Contriol. It's a small "motor" or solenoid that controls the amount of air that passes thru the throttle body and into the intake and eventually into the cylinders. That along with the fuel injectors determines your idle speed. Input by varies sensors help the PCM (computer) adjust the IAC for a proper idle dependant on temp., load., etc.. They are a common item to be intermitant if they are going bad. A classic example of a bad IAC is truck will start if you hold the pedal down, but will run awful at say 500 rpm, and then just stall. Or it may stall going around a corner, but start back up if you hold the pedal down . You can try to clean them, which works for mine, but most of the time it doesn't work. Mine responded to "throttle body cleaner" sprayed into the throttle body with the engine off and holding the butterfly open. You have to remove the ductwork to do this(no biggie). Notice I didn't say CARB CLEANER. The inside of the throttle body has a coating that carb cleaner may disolve if sprayed inside. Some guys go ahead and do it, I prefer to error on the side of caution and use dedicated throttle body cleaner. A new IAC runs around a $100 bucks, most places have them. Hope I helped answer your question.

Spotty

 

My 01 did the exact same thing, replaced the IAC and problem solved.

 

If you're looking for the IAC, check out our website:

http://www.rockauto.com/catalog/x,ca...,parttype,5028

Thanks for looking,
Justin

 

thanks that helps alot i'm gonna try and clean the IAC this weekend when it warms up a bit, and see if it helps

 

Cleaning the IAC may help isolate the problem but I've never had any luck with it. Clean it, lube it up with some marvel mystery oil and see if the problem clears up any, then replace it if it turns out to be bad. It'll drive you nuts until you do.