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Chevy 350 tbi Backfiring

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  • Chevy 350 tbi Backfiring

    I have an 89 suburban with a 350 small block in it. The motor was rebuilt by a family friend about 60,000 miles ago. Recently it needed a new cap and rotor installed, after that truck ran perfect. About a week ago it backfired on me, just out of no were. About two days later driving to work and it dies for no reason. Now it backfires just about every time i drive it, but other times it runs perfect just rough idle. I know for shure it backfires out of the tbi but not shore if it does the exaust to. When it backfires it will not accelerat or anything just stays at about the same rpm no matter how much throttle i give it and I don't know what it could be??? Every other post ive seen only describes one part of my delema not all in one.
    Last edited by 89 suburban; 03-23-2011, 10:35 AM.

  • #2
    Re: Chevy 350 tbi Backfiring

    do you live close to an auto parts store that does testing on ignition modules?? my 94 was backfireing like a mother f'r about a year ago and i called around and everybody said it wasnt the ign module cause the truck still ran so i put about 150 bucks into it before i gave up and just bought an ignition module and that was my problem. mine was backfireing out of exhaust and tbi. mine idled a little rough like there was a slight miss too. hope this helps ya out.

    ps i know mine was backfireing out both cause you could hear a muffled backfire from tbi and then a backfire like a shotgun went off inside the truck cause i had true dual pipes with no glasspacks on it at the time


    Current Ride
    2004 Chevrolet Silverado 2500HD 4x4 6.0L

    Past Rides
    1997 K1500 ECSB Z71 5.7L 350 Vortec
    1994 K1500 ECSB Z71 5.7L 350
    1992 C1500 ECLB 5.7L
    1978 C10 RCSB 5.7L
    1969 C10 RCLB 5.7L

    Comment


    • #3
      Re: Chevy 350 tbi Backfiring

      Will do thx for the info! I hope thats it to! The ignition module is different from the ignition switch correct? Because i just replaced the switch.

      Comment


      • #4
        Re: Chevy 350 tbi Backfiring

        yes the module is different from the switch. its under the hood, part of the ignition system. back by the coil and distributer.
        looks like this, took from napa website.
        2006 Silverado Red/Silver *GONE BUT NOT FORGOTTEN*
        1992 Chevy K1500 SCLB (project in the making)
        1991 Chevy K1500 ECSB
        2004 GTO Purple/Purple

        Comment


        • #5
          Re: Chevy 350 tbi Backfiring

          it is actually under distributor cap. when you replace or even take off to test make sure both surfaces are clean and put a layer of dielectic grease on the bottom of ign module (its for cooling purposes) also when you take it off be carefull with the little 2 wire plugin with letters p and n by it cause wires are fairly short and they go to the pickup coil in distributor


          Current Ride
          2004 Chevrolet Silverado 2500HD 4x4 6.0L

          Past Rides
          1997 K1500 ECSB Z71 5.7L 350 Vortec
          1994 K1500 ECSB Z71 5.7L 350
          1992 C1500 ECLB 5.7L
          1978 C10 RCSB 5.7L
          1969 C10 RCLB 5.7L

          Comment


          • #6
            Re: Chevy 350 tbi Backfiring

            That is really good advice to have the EST checked. Also when thye check it ask them to run it through the test three or more times. If it fails any? Replace it. It is the only piece of these EFI systems that has a record of gremlins, works but has intermittent issues. Most everything else works forever or dies,no gremlins... HTH
            1998 Chevy Silverado 5.7L Vortec Auto PCM Black Box 0411 Swap and RoadRunner!
            1990 Chevy Suburban Silverado 5.7L 2wd ECM 1227747 HyWay Lean Cruise 18.5 MPG
            1988 Chevy ECLB C2500 5.7L 700R4 2wd ECM 1227747 HyWay Lean Cruise 17.8 MPG

            GearHead-EFI.com Tuning, Conversions and Transplants!

            Comment


            • #7
              Re: Chevy 350 tbi Backfiring

              Thank you for the comment Eagle-Mark. My ignition module when it started acting up it would only backfire like once a day for a while. then it would be fine for a week or so. then come back worse than the previous time.


              Current Ride
              2004 Chevrolet Silverado 2500HD 4x4 6.0L

              Past Rides
              1997 K1500 ECSB Z71 5.7L 350 Vortec
              1994 K1500 ECSB Z71 5.7L 350
              1992 C1500 ECLB 5.7L
              1978 C10 RCSB 5.7L
              1969 C10 RCLB 5.7L

              Comment


              • #8
                Re: Chevy 350 tbi Backfiring

                also check base timing. should be at zero degrees with est wire disconnected.
                O2 GMC RCSB 4.8L V8 AUTO 3.73's
                rebuilt/beefed up 4L60E(at 43,000miles)

                Comment


                • #9
                  Re: Chevy 350 tbi Backfiring

                  Thx everybody I got it fixed but it was the coil!!!!

                  Comment


                  • #10
                    Re: Chevy 350 tbi Backfiring

                    your welcome (even though what we said wasnt the problem lol)


                    Current Ride
                    2004 Chevrolet Silverado 2500HD 4x4 6.0L

                    Past Rides
                    1997 K1500 ECSB Z71 5.7L 350 Vortec
                    1994 K1500 ECSB Z71 5.7L 350
                    1992 C1500 ECLB 5.7L
                    1978 C10 RCSB 5.7L
                    1969 C10 RCLB 5.7L

                    Comment

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