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High Idle- long post

Discussion in 'Ford Trucks' started by ChevYooper, Oct 10, 2007.

  1. hey guys,

    I put a new Idle Air Control Valve in my 91 5.8L F250 today (i unpluged the old one and the engine didnt stumble so i figured it was bad). Sure enough the truck runs much better, but now she idles around 1400 RPM. I let it idle for about 5 mins and then drove it about 15 miles, and the trucks temp gauge didn't even reach "normal". If i pulled up to a stop with the truck in gear and my foot on the brake, shed idle around 600, but if put in P or N shed go back up to 1400 quick and stay there! If i shifted from D to R, shed idle up from 600 to 1400 fast and go into R real hard and drop back to 600. I am wondering if the fan clutch is shot, or if they (guy i bought it from) may have rigged the fan to run more because the plow would make the truck run hotter. I just put new coolant in (70-30% mix) in the truck too.

    Anyone have any thoughts????

  2. sorry for the long post.....

    Nothin though eh??
  3. hydro_37

    hydro_37 PlowSite Veteran
    from iowa
    Messages: 3,790

    Try www.ford-trucks.com
    Go to the forum pages and see which forum is best for your truck and problem
  4. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    I have an 89 --5.8, been through the same challenge with it a few times.
    Check the cruise control cable end it can come out of it's holder and not let the throttle return to the stop. Make sure someone didn't cut a slot on the back of the throttle stop screw so it can be adjusted out. Some people will do that so they don't have to replace the Idle Air Control.You could be getting too much air feed making the idle high. Could be your Throttle Position Sensor. Your Fuel Pressure Regulator could be giving too much pressure. Unplug the vacuum line when it's running the engine should speed up. You should hear the pump relay click on and the regulator will go " Vert" sound when it bleeds off pressure when you first turn on the key.The single model repair manuals have check out procedures for all the emissions and EFI parts. Try not to just replace parts, it will just make you even madder that it's not the problem!
    If it has the steel can style vacuum reservoir on the passenger fender liner, it may have rusted out. The emissions and EFI controls need good vacuum supply to operate.
  5. yamaguy

    yamaguy Senior Member
    Messages: 556

    I bet you have a vacuum leak somewhere. Check all of your vac lines. I would probably replace them since you just bought it and don't know the maintence thats been done.