Backfiring when let off gas

Discussion in 'Troubleshooting & Diagnosis' started by Newtoy78z, Sep 29, 2019.

  1. Newtoy78z

    Newtoy78z New Member

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    Just purchased a 78 Z28. I had the original exhaust manifolds replaced with headers and replaced both mufflers. She doesn’t miss a beat when idling just backfires when you let off the gas. Sounds like coming from driver side. Also sometimes she starts on 1st try other times takes a couples of tries. Any suggestions? Thanks
     
  2. bourbon_scotch

    bourbon_scotch Veteran Member Lifetime Gold Member

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    change the timing
     
  3. tom3

    tom3 Veteran Member

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    Sometimes an exhaust leak will cause the backfire too.
     
  4. mallard

    mallard Veteran Member

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    Backfire or a "rapping" sound? A loose muffler baffle can mimic that sound as well.
     
  5. ZEN357

    ZEN357 Veteran Member

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    Correct Spark Plugs?
     
  6. cadillac_al

    cadillac_al Veteran Member

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    Backfire like a rifle shot or minor lean popping?
     
  7. larrylarry

    larrylarry Veteran Member

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    Exhaust leak. Air is getting inside the pipe also could be a timing issue to.
     
  8. Vettenick

    Vettenick Vettenick

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    Other than the headers, is this car stock with any emission equipment still installed, like EGR ? Did you have this problem before the headers, or did it start right after the headers?
     

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