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Thread: 0300 code

  1. #1

    Default 0300 code

    I just got my 97 c1500 truck back from the shop. I got the 350 redone to a 383. I just put around 500 or so miles on it and it ran smooth. The other day I got in it went for a lil ride to my dads house and before I got there the thing started running like crap. It is showing 0300 code. Changed the cap,rotor, map sencor still no change. Not sure what it is. Need help. The engine is still breaking in.

  2. #2


    I personally can’t help but I did some looking around. Check out this thread. That code was brought up. Also in the search engine in the top right of this page put in code 0300 see if there are others. Sorry but that is all I can do.
    Tim Walters (Curky)

    Wrangler AT/S 265/70R17 - Trail-FX window vents - Husky fitted splash guards - Silver Star zXe - Leveling kit -

  3. #3


    P0300 is a random mis-fire code. Which usually means more than one cylinder is experiencing a mis-fire.

    Spark and the components that go with it can be one area that causes this problem. You changed the cap and rotor, how do the wires look?
    Rebuild probably means you used new plugs, did you get the correct plugs and were they good plugs (sometimes our engines don't like some plugs)?
    Other things that can cause a random mis-fire are cylinder compression and vacuum leaks.
    Could you have a lose head that is letting the compression leak by. A cylinder compression check will tell this.
    Could you (and, this is my best guess) have a lose intake manifold that is allowing a vacuum leak?

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

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