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Deiseling and weird idle on my first k-5 purchase

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by fourwheelinj1, Oct 30, 2002.

  1. fourwheelinj1

    fourwheelinj1 Registered Member

    Sep 18, 2002
    Likes Received:
    Wake Forest North Carolina,USA
    I just bought my first K-5 yesterday. It is a 85 with a 305 and manual tranny. Anyway when you first crank it, it idles at around 2000 rpm and if you wait a min and then pump the accelerator once it will fall back to around 1500. This seems normal to me, but then if you start to drive it the idle constantly changes. It will even idle at 2800 sometimes. I have seen it idle any where from 900 to 2800 for no apparent reason. The thing also deisels after you cut it off. It only does it if it has been drivin enough to get warm. While it is deiseling the choke light comes on. This is my first real experience with what i believe to be a crb problem, any help would be greatly apprecited.
  2. HarryH3

    HarryH3 1 ton status Author

    May 31, 2000
    Likes Received:
    Georgetown, TX
    Check to see if the throttle cable or any linkage on the carb is binding. Carbon buildup in the throttle bores can also cause the throttle blades to not return fully. Even something as simple as a broken throttle return spring can also cause it. Fix the problem with the idle speed and the dieseling should also go away. Having the throttle blades open when the engine is shut off hot can cause the dieseling. Many carbs had an idle solenoid that was energized when the engine was running, and held the throttle open just enough to get a good idle speed. When the engine was shut down, the solenoid would turn off and close the blades all the way. /forums/images/graemlins/cool.gif
  3. imiceman44

    imiceman44 1 ton status Premium Member

    Aug 5, 2002
    Likes Received:
    Sacramento, CA
    Another thing that could help, was the truck stting for a while? old fuel tends to do weird things like dieseling, and fluctuating Idle. Put some new gas in it and pour in a fuel treatment can, and check the above mentionned items and let us know what happens.

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