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98 chevy 2500 5.7l bi fuel surging on take off on cng

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  • 98 chevy 2500 5.7l bi fuel surging on take off on cng

    my truck ran great on cng until recently, i filled it with cng and it started running wrong as soon as i started it back up. it seemed to idle to low. when i gave it throttle the rpm surged up and down until i got to about 15 mph. it still does it and i notice it will do it in town if i get below 20 mph and go to speed up. if i don't ease into the throttle if i romp on it a little it don't seem to do bad. i changed my plugs,wires,cap and rotter last week, my old plugs and wires look fine but the cap and rotter had a lot of corrosion in all the contacts. i figured this would help a lot but it did not. does anyone have any ideas. it has the factory impco bi fuel system.

  • #2
    come on it has been months, someone has to have some ideas on why my truck would have a surge or hesitation when i am taking off.


    • #3
      Do you have a code reader for obd2 codes? If not get something (like a plx kiwi, scan guage or Chinese copy) that allows your smartphone to run the "torque" app. It will allow you to monitor a wide variety of obd2 engine parameters that might help identify your issue.
      If the truck runs fine on gasoline I would suspect your filters. What happens if you stomp on the accelerator at highway speeds?
      My first observation with the torque app would be the short term fuel trims as it surges.


      • #4
        I have a dual fuel chevy malibu. CNG using a impco mixer. I had the same type of problem. Turned out to be an intake air leak after the MAF sensor . I found the leak with a smoke machine.