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Thread: High/Fast idle device location?

  1. #1

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    High/Fast idle device location?

    What cause the engine to have a "fast/high" idle.

    My engine runs great, but idles around 800 constantly(hot or cold, may vary by 50RPM or so, going off top of my head)

    What controls the high idle as i thought it should idle around 1100-1250 when it is cold then drop down to 750-900 once warmed a little.

    Its a 86 Ford Ranger with a 4D55 incase anyone is wondering....

  2. #2



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    800 is correct. That's on the money there should be a screw on the side where the linkage is that would adjust your throttle
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  3. #3

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    Quote Originally Posted by camoit View Post
    800 is correct. That's on the money there should be a screw on the side where the linkage is that would adjust your throttle




    For those of us who know better this is not what the OP was asking about. There is no automatic high idle control on the 4D55 engine. The high idle could be caused by several things but I would not consider 800rpm high idle. Check your A/C switch. If it is turned on it will cause a high idle. Also the high idle can be controlled by a throttle control under the left side of the dash. More or less the high idle control is manually controlled on the Mitsubishi and Dodge diesel pickups.

  4. #4

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    Quote Originally Posted by 4D55 Performance View Post



    For those of us who know better this is not what the OP was asking about. There is no automatic high idle control on the 4D55 engine. The high idle could be caused by several things but I would not consider 800rpm high idle. Check your A/C switch. If it is turned on it will cause a high idle. Also the high idle can be controlled by a throttle control under the left side of the dash. More or less the high idle control is manually controlled on the Mitsubishi and Dodge diesel pickups.
    Actually the ranger has an idle control in the forum of coolant through the IP pump. 750 is factory spec on the idle. There is a screw on the side of the pump facing the engine that has contact with the throttle lever (Usually has red stuff on it) that can be backed off. As these injection pumps wear out there will no longer be a cold start function. Note : This it different cold start function than the mitsubishi / ram 50 4d55 which operates via a cold start throttle cable.

  5. #5

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    Ooops, I missed that it was a Ranger.

  6. #6

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    yea it is constantly 800 and i thought it should idle around 1000-1200 when cold... so there is some sort of screw facing the engine that is operated by coolant temp?

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