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Thread: Help! LS3 Swap Running Issues

  1. #1
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    Aug 2020
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    Default Help! LS3 Swap Running Issues

    Just finished an LS swap and having running/idling issues. I am new to EFILive and tuning in general. Hoping someone can take a look at the tune file and a short data log and offer some insight and possibly spot any issues that is keeping this thing from running.

    The swap consists of an 07 L92 Escalade motor put in a 86 Porsche 944. The only mods made were an LS3 intake, Bosch 42lbs injectors, Ls3 DBW throttle body, Holley sniper fuel rails, stock Corvette pressure regulator and headers. Basically converted to an Ls3 keeping the VVT. All sensors are stock minus the MAF, O2's and MAP which are new stock LS3 parts. The car has a stock manual 5 speed with an aftermarket VSS sensor. I used a standalone harness, E38 ecm and Corvette DBW pedal from PSI. The ecm was supposedly flashed, VATS removed etc with a base tune for all the above parts. The car currently does not have an exhaust, running through open headers. I installed header extensions with bungs for the O2's.

    The car fires right up, idles poorly for 10 seconds or so and then starts surging and sputtering. I can keep it running for a bit by playing with the gas pedal, but ultimately I loose the pedal completely and it dies. Running pig rich and fouling the plugs only after maybe a minute of run time.

    The only DTC I am getting is a MAP sensor code. I checked the sensor and ref, signal, ground voltages seem to check out. KOEO kpa is around 100 and KEOR is around 50 which seems right from my reading.

    A buddy managed to download the tune file and a short running data log with EFILive. Files attached.

    Thanks in advance guys!
    Attached Files Attached Files

  2. #2
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    This is an 08 Corvette manual tune which will not support VVT and the tune is not setup for it either. I downloaded a stock 08 Vette tune from the DropBox (click here) and compared it to your tune. I'd suggest you download it and look through the changes as well.

    Your tune has 42lb injectors, throttle body updates, skip shift disabled, bunch of DTCs adjusted for standalone use, no cats or post-cat O2s, looks like fans setup [likely via HPT] for discrete fans, clutch signal disabled, and some speedo changes. VATS isn't disabled, but since you're getting it to actually run, it may not need to be? (This seems odd to me.) It's using a factory LS3 MAP and MAF settings which aligns with what you've got installed.

    There are no MAF or VVE changes, which explains why it runs poorly with larger injectors. If you have the stock injectors, I'd suggest putting them back in, updating the tune, and trying that to see if it will idle better.

    How does it run with the MAF unplugged?
    What's your wideband O2 say? If you don't have one, you'll need one to get the tune dialed in.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, tuned, turbo mods, etc.
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

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