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LO GAS 5.3l #1 and #7 Cylinder misfire

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  • LO GAS 5.3l #1 and #7 Cylinder misfire

    Hoping that someone might have more expertise than we do. Background, Lo Gas CNG conversion, installed by certified ASE and CNG tech, on gasoline the Tahoe runs fine, but on CNG, has bad #7 misfire between 700-2000 rpm, and occasional #1 misfire, all the normal stuff has been replaced, injectors, plugs, wires, coilpacks etc. I rode with my brother in law to check it out, feels to me like plugged cats, but once its switched over to gas, no problems, and runs the same with full or partial fill in CNG tank.

    Was an aspirated kit but was switched over to this multi port injection because the old kit would die out at random times, i thought maybe changing out the to a colder plug on the #7 cylinder might help, but this is really not my area of expertise,

    Any ideas or suggestions would be super appreciated

    Have a great day!

  • #2
    Re: LO GAS 5.3l #1 and #7 Cylinder misfire

    I would do a cylinder leak down check, it sounds like it could be a recessed valve seat.