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Thread: LS Swap, '57 Chevy, misfires, pops, see issue in scanner, need some guidance...

  1. #1

    LS Swap, '57 Chevy, misfires, pops, see issue in scanner, need some guidance...

    Trying to help a buddy with an LS swap '57 Chevy.
    Junkyard 04 GTO LS1

    UPDATE

    Car refuses to idle and still backfires. I logged misfires by cylinder and see a large number on #7 and some on #2. Plan to replace coil on #7 and swap injectors and coils if that doesn't remedy.

    Fuel Pump replaced after observing erratic fuel pressure drops at rail...now holds 58psi as expected
    Did verify via noid lights, all injectors are getting signals from ECU
    Plugs and wires have been replaced with OEM wires and TR5s
    MAF replaced
    TPS Replaced
    Cam sensor replaced (this allows the engine to at least run now from 1500-5000 without stumbling or backfiring)
    Removed and reinstalled intake (to swap cam sensor) and made sure intake gaskets were intact and manifold torqued correctly.

    Would misfires like this cause the engine to backfire horrendously at idle? Anything else I'm missing, am I still chasing ground gremlins?

    This thing is really frustrating me to say the least.

    Latest Logs and Tunes attached. Really appreciate any help!! Cool car just need it to run! Been almost 10 years!!




    On first start, the motor ran horribly, backfiring and barely idling.

    B1 (Driver's) is showing Super Lean and then spikes of fuel.

    Here is what I know and the data I have:

    PSI - LS Swap Harness
    PSI - EFI Tank 255LPH Pump
    PSI - Gauges
    04 GTO Complete (Tune File and Scan Attached)
    Injectors were cleaned and flowed by Injector RX
    Fuel Rail was dirty and cleaned by injector RX
    Corvette Style Filter/Regulator
    When I first plugged into the car I couldn't get any data - realized the only grounds that had been connected were to the block and the PSI harness to drivers cylinder head.
    Ran all the grounds per PSI tech sheet using correct AWG, hydraulic crimps, sanded surfaces, star washers.
    New battery

    Not sure why B1 is so lean and only randomly delivering fuels spikes.

    Plan to go get Noid set next.

    Why don't I see Duty Cycle or PW on injectors?

    Thanks in advance for any help!!
    Attached Files Attached Files
    Last edited by Closer_2001; 11-22-2021 at 09:57 AM.
    '18 Sierra L5P
    '03 Sierra 4.8/NV 3500: LS6 Cam, HPT Tuned
    '15 Explorer Sport - SCT, AEM (Wife says...it feels faster??)
    '01 Z06

  2. #2
    Tuning Addict 5FDP's Avatar
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    You have to log what you want to see. No injector pulse width being logged means no data being spit out.

    Bank 2 has a code P0155 present in that log and it's flat lined at 450mv, so there is a circuit problem with that.

    You also have a ignition coil code P0358 in that log, so look into that. And a P0102 for the MAF sensor.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
    Quote Originally Posted by 5FDP View Post
    You have to log what you want to see. No injector pulse width being logged means no data being spit out.
    What would cause this? TY for the reply.
    '18 Sierra L5P
    '03 Sierra 4.8/NV 3500: LS6 Cam, HPT Tuned
    '15 Explorer Sport - SCT, AEM (Wife says...it feels faster??)
    '01 Z06

  4. #4
    Tuning Addict 5FDP's Avatar
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    I thought that was kind of in my answer. You see no data because you logged no data. The injector pulse width avg for banks 1 and 2 are not in the channels list on the left, thus no data to be seen.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  5. #5
    Quote Originally Posted by 5FDP View Post
    I thought that was kind of in my answer. You see no data because you logged no data. The injector pulse width avg for banks 1 and 2 are not in the channels list on the left, thus no data to be seen.
    Apologies, I let the scanner gather the available PIDs and deleted anything that was grayed out. I will re-add manually and see if there is simply no data being reported. My question should have been...if the scanner isn't picking up the PIDs and when I add them manually no data is being gathered, where next. Thnx
    '18 Sierra L5P
    '03 Sierra 4.8/NV 3500: LS6 Cam, HPT Tuned
    '15 Explorer Sport - SCT, AEM (Wife says...it feels faster??)
    '01 Z06

  6. #6
    Latest Logs and Tune File
    Attached Files Attached Files
    '18 Sierra L5P
    '03 Sierra 4.8/NV 3500: LS6 Cam, HPT Tuned
    '15 Explorer Sport - SCT, AEM (Wife says...it feels faster??)
    '01 Z06

  7. #7
    Tuning Addict blindsquirrel's Avatar
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    Meridian MS
    Posts
    7,643
    Diagnose your DTCs first. Trying to 'solve' a wiring problem or failed sensor by fiddling the tune file is a path straight to misery.

    P0358
    P0155
    P0300

  8. #8
    Quote Originally Posted by blindsquirrel View Post
    Diagnose your DTCs first. Trying to 'solve' a wiring problem or failed sensor by fiddling the tune file is a path straight to misery.

    P0358
    P0155
    P0300
    TY - I was looking at the crank relearn scan and those codes don't show up...odd. They are there on the startup where the car was violently backfiring. Going to swap #7 coil and determine issue with 02. Oddly, lean condition is in Bank 1 not Bank 2, 02 heater failure code is for Bank 2. Assuming misfires might be throwing off the fueling on Bank 1.
    '18 Sierra L5P
    '03 Sierra 4.8/NV 3500: LS6 Cam, HPT Tuned
    '15 Explorer Sport - SCT, AEM (Wife says...it feels faster??)
    '01 Z06