My 1991 F150 suddely developed an idle of about 2500rpm. If I pull the two wire connector off the "Idle air control motor" or something like that, the idle goes back to normal. What is giving it the signal to idle so fast?

 

Welcome to FTE!
I would recommend getting a book for your truck, and tracing out the wiring. Also, it could be that the throttle plate was adjusted at some point. Is the check engine light on, if so what codes can you get out of it? Has the truck always done this, or just recently? Any recent work? Post again with this information.

 

This just started, no the check engine light is not on. One other thing, it's reluctant to shift to the next gear. I did not find any obvious vacuume leaks, hoses on and tight.

 

If it is an automatic, be sure to check the vacuum line down at the modulator valve- that may be off.

 

I always recommend starting by pulling the codes, even if the CEL isn't on. You should also check the vacuum.

 

Well I broke down and took it to the Ford dealer and they said it is the processor so I ordered a replacement ($300). I'll let you all know if it works out.

 

I have the same problem, my 1995 F150 started idling approx
2k. The first time I took it to a Ford dealer they couldn't isolate the problem because it was intermittant. I had the fuel injection serviced the other day and when I went to pick it up the idle was
really high...Any help is appreciated!!!

 

I replaced the processor and it made no difference. Ford is now into my pocket for $350.00 and I still have the same problem. I wonder if they will own up to their mistakes and refund me what I spent so far, I have a call into the service manager, waiting for a call back. Will keep you posted.

 

I just dropped my truck at the dealer this morning. I advised the service supervisor that I had brought it in last week for a
fuel injection service on his recommendation because of the intermittant high idle, and the service was needed and it could fix the problem. I did express my displeasure with them for not telling me that the idle was up at 2k after they had serviced it (did an engine detail also) and that the idle was fine when I brought it in. I just want to know what the problem is, without spending a bundle of money...

 

If you have a friend at a Ford dealership, I would have them take a look at the readings for the TPS, the Intake Air Temp sensor, and the Coolant Temp Sensor. If any of these are out of range, the computer can think it's running too cold, or at the wrong throttle angle. None of these would necissarily turn on the check engine light, but they may throw a code. If you don't know someone at Ford, and you decided to take it back there, tell the service writer that you want a senior tech to work on it. I know the Ford dealer here will hire just about anybody off the street to turn wrenches, so the chances of somebody just walking in and getting a good tech are slim. Also, do either of your trucks run ok when cold? Have you checked to see if the tranny kickdown linkage is sticking or anything?

 

You hit it on the head! I got called from the dealer and the service mgr said he has his "best" tech on the job, and when I had my engine detailed they got water or something on that TPS and that the readings were off...don't have the paper in front of me to tell what the exact verbage was but, they also told me that
I will need about 535$ more work, something to do with the throttle....After they did the adjustment and replaced the part the idle is now fine. Also the my truck did run ok in the winter...
Thanks for the info....

 

I SURE WISH I HAD A FRIEND AT THE FORD DEALERS SERVICE DEPARTMENT!!! I guess I'm not as trusting as I should be. The service manager decided the processor I bought was defective and to bring it in for a replacement. I should have it before the weekend. I just find it suspecious that the truck acted exactly the same after installing the replacement processor. For Ford_Six, I did not see any of the codes from my first visit to the Ford dealer so I couldn't tell you about the temp readings and before this started it did run OK in the cold (as cold as it gets here in California). What is the tranny kick down linkage and where is it located. Along with the high idle the truck also has a reluctance to shift to the next higher gear. Could it be related?

 

$350 for an EEC is a RIP-OFF!!! Every dealer around me only wants $250, and the parts stores sell remans for as little as $180. But I find it hard to believe your EEC crapped out and the ONLY symptom is a high idle. Pull the codes yourself - if you go to the link in my first post, all you need is a paperclip. I bet you'll find either a vacuum leak or a bad IAC.

 

The tranny kickdown for your truck is a cable mounted to the throttle assembly. If you have cruise also, there will be three cables going there- one that goes back to the speed controller, one that goes to the gas pedal, and one that runs to the tranny. I would pop the tranny one off, and see if it operates smoothly, without excessive resistance. I wouldn't drive around with it disconnected, though, as that can damage the transmission.

 

The intake manifolds on these trucks are famous for sucking the gasket between the upper and lower manifolds sometimes they will suck small pieces and cause High Idle problems!!!!!!!!!!!!