Results 1 to 5 of 5

Thread: LS1 backfiring under 1,000 RPM

  1. #1
    Potential Tuner
    Join Date
    Oct 2019
    Posts
    2

    LS1 backfiring under 1,000 RPM

    Hey y'all, I'm new to tuning and I've ran into a bit of a snag. For the last few years, I've been working on rebuilding an LS1 to swap into an '87 trans am. Motor is all stock except for a torquer v2 camshaft (232/234.600"/.600" 112 LSA), valve springs, and hardened pushrods. Now that I finally have it back together and In the car, I can't really get it to run right. My issue is that the engine backfires under 900-1000rpm, and flat out refuses to run under about 750rpm. I'm running it off the stock tune which I'm sure doesn't help much but I am unsure what parameters to adjust and figured I should ask for help before I blow something up. Attached are my log and tune files: Factory Tune NO VATS.hpt Runs but backfires.hpl

    Any help would be greatly appreciated, thank you!

  2. #2
    Tuning Addict 5FDP's Avatar
    Join Date
    May 2012
    Location
    Rogers, MN
    Posts
    13,533
    Plug your IAT sensor back in, that is causing it to use extra fuel.

    Get a wideband o2 sensor on this car as soon as you can too.

    With it being a swap car, go through the tune and disable features you are not using anymore. Like rear o2 sensor codes, EVAP codes, cat codes. Disable cat over temp protection.

    Don't expect it to run that well or even want to idle well until the fueling is corrected. The MAF and VE need to be gone through with a wideband to get the airflow model back in check.

    Also make sure you have ZERO vacuum leaks and exhaust leaks. And double check that fuel pressure is at spec, that being ~58psi.
    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
    Potential Tuner
    Join Date
    Oct 2019
    Posts
    2
    Hey, thanks for the input! I connected my IAT and noticed no difference. I have disabled some of the unused features, such as the rear o2 sensors, but I still need to go back and disable EVAP and cat codes. I have checked for vacuum and exhaust leaks and found none, so I should be good there. As for the wideband, I still need to buy one, any recommendations?

  4. #4
    Tuner
    Join Date
    Dec 2018
    Location
    Washington State
    Posts
    182
    Quote Originally Posted by CMutt8145 View Post
    Hey, thanks for the input! I connected my IAT and noticed no difference. I have disabled some of the unused features, such as the rear o2 sensors, but I still need to go back and disable EVAP and cat codes. I have checked for vacuum and exhaust leaks and found none, so I should be good there. As for the wideband, I still need to buy one, any recommendations?
    Get an AEM X Series.

  5. #5
    Tuner in Training
    Join Date
    Jun 2019
    Posts
    23
    not saying this is your problem but I experienced this with my 2000 ls 5.3 fresh build and after replacing push rods to different length new injectors plugs wires etc etc fix = I had the #1 bank injector wiring on the wrong injectors 1 was on 5 5 was on 3 etc so it was sending fuel to a cylinder that wasn't getting spark at that millisecond of time causing unburnt fuel to ignite causing my backfire not sure if your year has 8 injectors 8 coil packs etc