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High RPM problem on CNG

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  • High RPM problem on CNG

    High RPM's on CNG causing bogging and backfire.

    I am having a backfire issue only when the RPM's are over 5000. For example, when driving up a hill and having to pass a vehicle, I step on the gas and the car kicks down into a lower gear and then feels as if it is bogging down and is very loud and shakey. The 5000 or above RPM is only reached when I have to step on the gas around 50 MPH to 65 MPH. I have blown 2 air filter covers and replaced the plugs inbetween blowing the last cover. I didn't replace the wires because they looked almost new. Has anyone experienced something similar or can anyone explain why I can't run on CNG at or above 5000 RPM? I let the CNG run out and tried the same thing on gasoline and the car would bog down and shake a little at that high RPM but no backfire. Any ideas?

    Thanks in advance.

    So sorry, I was so caught up with the problem I forgot the details. 2001 Chevy Cavalier, 126k miles, 2.2L engine and runs great when I don't have to go over 5000 RPM.

    I hope this helps.

    Last edited by wacbass; 10-28-2008, 09:58 PM. Reason: Forgot the details...

  • #2
    Re: High RPM problem on CNG

    Ok, what are we working on: make, model, year, engine, cng system, body style, vehicle load.

    Sounds like you're running lean, backfire and all. You might want to put a pressure gauge on the low pressure side of the and see what the pressure to mixer or injectors is



    • #3
      Re: High RPM problem on CNG

      I'd replace your wires before you try anything else. ( I already said this in your other post)

      You can also read more HERE

      Everyone I know who ever had backfire issues (especially when they occur only in CNG and not gasoline), found that it stemmed from bad plugs or wires.

      Wires are cheap and easy. Start there, and if it doesn't cure the issue, then we can move on to some real trouble-shooting.


      • #4
        Re: High RPM problem on CNG

        It sound like the car is running lean, mite be injectors or something as simple as a filter. Being lean can cause both your issues.
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        • #5
          Re: High RPM problem on CNG

          I will try the wires and change the air filter to see what happens.

          It blew a box again today when I had to speed up while entering the freeway to avoid another vehicle.

          Thanks for the help. I will keep you posted.