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Bad idle

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  • Bad idle

    Maybe somebody out there can help with the latest problem. Car is a 2001 Cavalier bi-fuel. The vehicle idles terribly while on CNG. If on gasoline, no problem at all and if under load (20 mph+) while on CNG no problem either. Slight smell of natural gas coming from the engine bay, and OBDII code indicates the engine is running too lean. Should I be looking at the low-pressure regulator with these symptoms and if so, is anything on it serviceable or should I plan on replacement of the part?

  • #2
    Re: Bad idle

    sounds like low pressure reg to me, but check your plugs, that you are not using platinum plugs

    2003 Hummer H2 bi-fuel
    2000 GMC Yukon XL bi-fuel
    1999 International 4700 dual-fuel
    2007 Chevy Avalanche bi-fuel

    FMQ2-36 Fuelmaker w/ 24 GGE cascade


    • #3
      Re: Bad idle

      Are platinum plugs not to be used in these vehicles?


      • #4
        Re: Bad idle

        I had a similar problem, and in addition I would occasionally get a backfire when accelerating. I replaced my plugs and plug wires and it went away. Somone told me though to use the cheapest plugs, because more expensive plugs didn't work well with CNG. I don't know if that is true, but my cheap-o plugs seem to have cured the problem, (although I did have a slight backfire the other day while starting... anyone know if that is normal?)



        • #5
          Re: Bad idle

          I had the backfire going on but it was during deacceleration. I looked at the exhaust mainifold and there was one loose bolt and one missing bolt on cylinder 4, and the 2 bolts that link the mainfold and the cat were loose. I tightened all of these and the backfiring immediately went away. Wouldn't hurt to make sure everything is tight and snug in your exhaust, if you haven't already done so.
          Replaced the plugs & wires and it does run a little better, but I still think that the main culprit is the LPR. I've heard they're rather expensive so I'm contemplating how economic it would be to replace, considering the very high mileage of my car. If I was in Utah, home of .69/gge, I would definietly repair just about any broken component on the car!


          • #6
            Re: Bad idle

            Quck question about plugs... I was told to get the very best and most expensive platinum plug for CNG cars. Tie at Intergalatic was the one that told me to do this, but you guys have me wondering. I haven't had any issues with these plugs, I didn't have any problems to begin with, but the old ones were pretty bad and it was time for new ones anyway.
            2000 Escalade (option 3 conversion) FOR SALE
            2004 F150 XLT (OEM conversion)
            2000 Camry (Awesome Car!!)


            • #7
              Re: Bad idle

              Sounds like the low pressure regulator to me.

              Available from gmpartsdirect.

              The LPR Part Number is 52369142, $290.54 from

              Good luck

              p.s. it's a snap to replace, 10 minute job.


              • #8
                Re: Bad idle

                Forgive my ignorance... Is the LPR the round unit on the top of the engine, passenger side? If so, what's the rectangular unit next to it?

                Edit: ....question is about the Cavalier
                Last edited by Runner; 12-22-2007, 09:47 AM.