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Thread: C4 problem

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    Default C4 problem

    Hey everyone. New to the forum here and looking for some help or advice. 1986 C4 with an idle problem. Over the winter I changed the valve covers, gaskets and plugs. After getting it back together, I noticed the idle wasn't right. It has ran kind of rough since I have had it, but worse now. Hard to start. Have to keep engine revved for a few mins and get it warm to idle. At times, it will miss out and the warmer it gets, the higher the idle gets. Any ideas?

    Thanks,

    Greg

    Indianapolis, Indiana

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    Moderator catbert's Avatar
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    Injection? Dirty Fuel?, fuel filter? Run a double dose of Techron in a half tank of gas. If there is an improvement, look further at fuel system. If not, start checking electrical.
    There are times for thinking, and times for acting, but the art is in the balance


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    I have had the injectors tested with an OHM meter and say they are good. I have put some Lucas gas treatment in it and a half tank of gas, but due to the rain I haven't driven it much since to work it all the way through. I have sprayed throttle body cleaner and wiped off the throttle plates. Could the IAC be bad? EGR valve?

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    Quote Originally Posted by Gvinson View Post
    I have had the injectors tested with an OHM meter and say they are good. I have put some Lucas gas treatment in it and a half tank of gas, but due to the rain I haven't driven it much since to work it all the way through. I have sprayed throttle body cleaner and wiped off the throttle plates. Could the IAC be bad? EGR valve?

    Could be, but I'd still replace the fuel filter for sure, and still use a bottle of Techron in with the Lucas. Techron is actually factory recommended, and has been proven to remove deposits in independent testing. Run the half tank with the double dose through, and see if there is an improvement, but if it's the fuel filter, nothing will help, except a new fuel filter.
    There are times for thinking, and times for acting, but the art is in the balance


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    Make sure you don't have a vacuum leak. A cracked, broken or NOT connected VACUUM hose WILL make it "Run like cr@P." Then check that your firing order is correct. It's easy to mix up a couple plug wires. YOU DID gap the plugs.....Right?
    Base timing in the neighborhood of 8*BTDC.
    On a vacuum gauge you should be pulling about around 18" of manifold vacuum at idle.

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