Alright guys, here's the deal. My battery went dead about a week ago, I jumped it off drove to work, dead again, jumped it off and drove to the shop and had the battery replaced. Ever since then the truck has had a low idle in drive while stopped at a light. I thought it may be the computer relearning the idle speed and stuff, but it's been about 300 miles now. The truck runs fine, then when you stop at a light the RPMs drop down to about 400, stay there for a couple of seconds then surge to 700 to 750 then settle in around 600. It doesn't do it at every stop either. Any ideas?

 

The idle fluctuation sounds like the IAC (Idle Air Control) valve is malfunctioning. It's located between the throttle body and the firewall. Get a preferred customer discount at your Ford parts counter...should be about $60 unless you're still under warranty. You should be idling in Park at 720 rpm and 600 in Drive.

 

had something like that on a 91 5.0 stang. the MAF sensor was bad, see if you can get the puter scanned.

 

I second the IAC, or maybe test your TPS (Throttle position sensor) I cleaned my IAC last week as it was coated pretty bad with carbon.

Fade

 

I know exactly what happened. The reason he didnt see the oil is because there was little or none in it to begin with. I don't know for sure, but i KNOW on my mothers expy it burns oil or something like no tomorow. Take 3 qts between oil changes, no smoke, no sooty oily tailpipe, its just not there. So i would venture to guess thats what happened here. And at that particular point in time, it was on its last drop. I hope there isnt a spun bearing, those are no fun. I had 4 on my 70 442---guess who's fault that was---somone drove the pi$$ out of it.

 

I had the same thing off and on the last few years, it seems to stop right after I remove the IAC and clean it each time. I just did this "repair" two days ago lately, and it stopped the dropping idle. I also cleaned the TB plate, MAF sensor, K&N filter, IAT sensor, and tightened up the fipk hoses. It seemed to help alot and the truck feels like it has more power/throttle respnse. I cleaned the IAC a little differently this time. I used a small flat blade screwdriver to gently pry the stopper up and cleaned the surface of it with TB cleaner and a Q-tip. I then let it dry out thoroughly, and re-installed it. The "stopper" is kind of wedge shaped, you'll see when you remove it. Good luck!,,,,98