my 1991 ford f-150 5.8l has been idleing funny and it does not always kick down after driving it on cold days. My main guess that it is the idle air control valve. Or is it some thing else that could cause this. How should i fix it.

 

While its idling to high unplug the iac, if the idle stays high its probably the iac. If it comes down then its being commanded high by the pcm. Your tp sensor could be going bad. Tp mode should read CT(closed throttle) at idle. If it reads PT(part throttle) even with the throttle closed then iac percent will be commanded up and cause the idle to be too high.

 

thanks for the reply i did what you said and the idle went down. Where is the tp sensor. Keep in mind that it does not do it every day.