I have a 91 f150 5.0 5speed manual tranny. The problem is that it idles way too high most of the time and in between shifts. For some reason the computer seems to be telling the IAC Valve to stick open or stay there for awhile. When I go to shift and push in the cluch once disengaged the engine revs up to 2500 or 3000. Its a relly annoying problem. Its not the IAC because I put a new one in, And it also isnt the idle adjustment screw.
Also... It dosent relly do it on warmup cycle, Only after its warmed up.
Please help!!!

 

Maybe you have a vacuum leak? I'd also suggest pulling the codes. Do it yourself with a paperclip. The directions are on www.fordfuelinjection.com

 

My truck did the same thing. The bushings in the throttle body wear out and the valves stick open partially. I got mine rebuilt at NAPA for $45. That may be your problem.

 

Ill pull the codes when i get home.

 

try cleaning and lubing the tb also. clean the carbon out of it and spary wd40 or like onto the shaft bushing area.
may may not help. but for sure carbon in them causes propblems

 

the tb iss clean. The truck did it when the engine blew (#8 piston cracked). I had a new motor put in and it still does it. All the components are clean. When I pulled the codes with the old motor, i cant remember the number that came up but it saw something about a (open circiut or SAW) . All the vaccum lines are good. I'll pull the codes with the reader when I get home. Think it could be the Distributor control module malfunctioning. I tried putting a different computer in and it did the same thing.

 

I have a '92 F-250 5.8 and I am having a VERY similar problem, I also was told to try the IAC Valve and am hopeing to get a chance tonight. But I like yourself am at a loss. Someone help us...

 

I have a 1993 F-150 5.0 manual transmission and am also having an almost identical problem. Many repairs but no fix.

 

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Had this exact problem for a while...no codes, no vacuum lieaks couldn't figure it out for the life of me. Try this...when this idling condition exists, pop the hood and try to physically close the throttle body by hand. If the condition stops, chances are the return springs for the TB are shot. I stuck an old carburetor return spring on there and haven't had the problem since. The gas pedal is a little bit harder to push though. Give it a try, can't hurt.

 

I have same problem as well, but does not go above 1200 rpm, then quick hit the pedal and goes down. My engine as well blew #8 piston @114,000 miles. I cleaned the TB and put new return spring on and helped as well. I still have a EGR stuttering problem that I think fried the old engine, I think. 5.0L/5spd.man. also. Good luck.

 

I pulled the codes today and got nothing except a (power steering pressure code). I cleaned the TB and put a return spring on and it didnt help any. Im still at a loss. I then pulled the wire going to the IAC and it juns soo much better. This isnt a fix but it does tell me that something is telling the IAC to open and stay there sometimes. Im going to put a Ford Motor Sports MAF Conversion kit on soon anyway. Mabe that will help fix the problem. Anybody elese think so or know of good results from a FMS MAF conversion? Thanks

 

I have a '96 5.0 and have very simalar issues. Mine already has MAF. Still haven't figured it out yet. It seems to be an all too common problem on these trucks that no one ever figures out. I am just waiting for it to get worse then maybe it can be diagnosed.