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  • Backfire at idle

    Just fired up my car with the ProFlo4 on it. At idle it pops out the exhaust. Add any throttle and it goes away. Only at idle? Any ideas? LSX454
    Attached Files

  • #2
    Not an expert,but the battery at 11.8 is concerning.

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    • #3
      IAC at 48% is a concern also.

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      • #4
        Originally posted by CorkyE View Post
        Not an expert,but the battery at 11.8 is concerning.
        For some reason it’s bouncing from 11.6- 12.0 gonna swap the battery out tomorrow.
        Last edited by Claykennedy; 08-28-2020, 08:00 PM.

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        • #5
          Not an expert either but I would expect to see more than 10* timing advance at 1100 rpm. Try raising the advance to the 15-20* neighborhood and see what happens. Do this before trying to get the IAC down in the 5-15% zone. Test the battery voltage with a good multimeter to verify voltage.

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          • #6
            The app always reads 1-1.5 volts lower than it is. Why is your idle so high?

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            • #7
              Originally posted by Claykennedy View Post
              For some reason it’s bouncing from 11.6- 12.0 gonna swap the battery out tomorrow.
              I would run a extra 10-12 guage charge wire from the alternator to the battery as a test to see if that improves it.

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              • #8
                Originally posted by Heatsoaked View Post
                The app always reads 1-1.5 volts lower than it is. Why is your idle so high?
                Checked it at the battery. It’s good. The tablet is just reading low as you said. I had turned the idle up trying different things. I’m stumped.

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                • #9
                  Did you unlock the timing?

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                  • #10
                    Originally posted by 1968CamaroGuy View Post
                    Did you unlock the timing?
                    Yes. even tried to advance idle to 17. Still pops at idle once warmed up.

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                    • #11
                      Originally posted by marc s View Post

                      I would run a extra 10-12 guage charge wire from the alternator to the battery as a test to see if that improves it.
                      Did that tonight. No change. Charging good and good battery.

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                      • #12
                        Originally posted by R573CAR View Post
                        IAC at 48% is a concern also.
                        The IAC is kinda all over the place. It’s hard to get it steady with it popping. Can’t adjust it until the motor is warmed up and that’s when it starts popping.

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                        • #13
                          It’s running very rich at idle. Cleans up when I give it gas. Seems kind of sluggish but does clean up.

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                          • #14
                            If I have the idle spark advance set at 17 at 1200 rpms should it be at 17 at 900 rpms mine shows 5?
                            Attached Files
                            Last edited by Claykennedy; 08-31-2020, 07:53 PM.

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                            • #15
                              I have my SBC set at 20* for idle spark. I had it at 15 and it made a big difference when I bumped it up to 20. 5* is way too retarded.

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