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97 f250 with 5.8 funny idle

Discussion in 'Ford Trucks' started by Kwise, Feb 20, 2010.

  1. Kwise

    Kwise Senior Member
    Messages: 123

    My 97 f250 5.8 heavy duty sometimes idles funny. It does not idle rough, but rather the rpm fluctuates up and down. It only does this in reverse or drive, while at a standstill or moving very slowly. When I put it in neutral or park, it idles fine. I suspect the egr valve. Has anyone had this problem?
  2. Milwaukee

    Milwaukee 2000 Club Member
    Messages: 2,180

    Are you use motorcraft dist cap, rotor, and spark plugs? That what cause my F250 run like that.
  3. Kwise

    Kwise Senior Member
    Messages: 123

    I think so. If they aren't, how would that affect it? It's only been doing this for a few months.
  4. PatriotLawnCare

    PatriotLawnCare Junior Member
    from WV
    Messages: 8

    First check obvious stuff. Make sure your cap and rotor are in decent shape, make sure your plug wires are actually plugged in correctly. I bought a 95 once that supposedly had bad engine troubles and only needed a tune up and a tps. Look underneath and see if the plumbing for the EGR valve has rusted out or separated. I've seen a couple of these that the tubing for it has rusted and then broke causing a bad reading on the sensor. Have you pulled the codes? Not all diagnostic codes will throw a check engine light. They may point you in the right direction. Good luck
  5. Milwaukee

    Milwaukee 2000 Club Member
    Messages: 2,180

    not use motorcraft parts can cause this issues. It no fun when you found that auto zone's dist cap and spark plug wires are garbage and cause short out.
  6. affekonig

    affekonig Senior Member
    Messages: 909

    Idle air control valve
  7. FordFisherman

    FordFisherman PlowSite.com Addict
    from 06611
    Messages: 1,613

    I thought the IACV was a 5.4 problem? I just replaced mine; truck sounded like a foghorn. To the OP- check that your vacuum lines are not cracked/disconnected also.
  8. affekonig

    affekonig Senior Member
    Messages: 909

    I've had the same issue on a few 5.8s and it always worked for me if I remember correctly.
  9. hydro_37

    hydro_37 PlowSite Veteran
    from iowa
    Messages: 3,790

    Sounds like a vacuum leak
  10. tuna

    tuna Senior Member
    Messages: 488

    IAC or TPS most likley IAC.
  11. blk90s13

    blk90s13 PlowSite.com Addict
    Messages: 1,157

    spray carburetor cleaner at your throttle body and see how it reacts that gasket is known to go bad I changed mine and cleaned the throttle body and it was running like a champ even since

    ( I owned a 95 f-250 5.8l 4 years ago )
  12. rpainetfd

    rpainetfd Member
    Messages: 44

    I have the same truck and had the same problem this winter. I EEC tested it and had a code for EGR excessive flow. Found the EGR valve to be sticking open just a little and the map sensor compensating. If you unplug the vaccum line to the map (black sensor on the firewall with one vaccum line) you can verify this. You can also verify this while it is acting up if you spray carb cleaner in the valve, it should smooth out. Mine was acting up in the middle of a storm and didnt have the time to change it. I held the plunger open with a screwdriver and sprayed it wtih carb cleaner. Than I ran some fuel injection cleaner through the tank. It fixed it 90%. Sometime between now and October I might change the valve. Good luck.
  13. Kwise

    Kwise Senior Member
    Messages: 123

    My mechanic suggested the IAC valve. I changed it out and it fixed it the problem...most of the time. It still acts funny sometimes but I think the IAC was bad. The EGR and all the obvious stuff looks ok. I'm content for now. Thanks for the advice everyone.