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Thread: LQ9/4L80e swap WOT/pedal issues

  1. #1
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    Jun 2023
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    LQ9/4L80e swap WOT/pedal issues

    Hello everyone, first time tuner here. I have a LQ9/4L80e swapped 97 Silverado that I have been tuning for a few months off and on (didn't drive over the winter). I have the basics like start-up, MAF curve and MAP tables done but I keep having an issue with some sort of throttle issue.

    The setup is:
    6.0 LQ9 from an 02 Escalade (with throttle pedal and throttle control box from the same truck)
    TBSS intake manifold
    LS3 throttle body (p/n 19420707)
    Torque Rush wiring harness adapter for the LS3 TB to 01/02 harness/
    Summit 8719 cam w/ springs

    The issue I've been having comes at WOT; the log shows up to 173% accelerator pedal position when I put the pedal the whole way to the floor. The log shows throttle position at 96% (what I have it limited to in the tune) yet accelerator pedal climbs all the way too 173% and the truck will HANG at 5k rpm and won't shift unless I lift off the throttle a few %. I'm assuming there's something to do with the pedal showing such high values as to why it's refusing to shift.

    The questions I have are:
    Do I have the right throttle body for this application? Torque Rush now lists the LS2 TB being compatible for this setup, not the LS3 TB - Are the differences in voltages a concern?
    Is there a calibration or re-learn procedure for the pedal control box? I can't find any info other than the adjustable pedals on the later Escalades.
    Could it be something to do with the transmission tune? The trans tune is basically stock and the truck drives totally fine under normal conditions.

    Any input or avenues to check would be greatly appreciated. Attached is my latest log and tune files.
    Attached Files Attached Files

  2. #2
    Potential Tuner
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    Jul 2021
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    I'm having similar questions regarding the readings from my throttle position sensor, only mine goes from 20 percent to 100 percent only. Does the tune rely on this tps reading for calculating airflow? You said it drives normally, even starting out with a tps reading of 96 percent? This seems like an arbitrary number, because my car seems to drive ok also. I say ok because I haven't got the idle dialed in yet - now I'm wondering if tps ratio makes any difference or not to airflow calculations. Otherwise, wouldn't the computer seeing 96 percent make the car idle really high? I don't know enough about this, but I want to learn more.

  3. #3
    Senior Tuner
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    Nov 2006
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    There are several trucks in the 2002-2007 time frame that 100% stock will read weird accel pedal positions up to almost 200%. This is normal.


    This sounds like the programmed shift points are too high. It goes by MPH first, then programmed RPM shift point.
    Tuner at PCMofnc.com
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  4. #4
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    Quote Originally Posted by Alvin View Post
    There are several trucks in the 2002-2007 time frame that 100% stock will read weird accel pedal positions up to almost 200%. This is normal.


    This sounds like the programmed shift points are too high. It goes by MPH first, then programmed RPM shift point.
    Thanks for the info man. I actually figured out the actual issue because the shift points correlated with the log and everything looked good there.

    For anyone else that may have this same issue, I solved the problem. When segment swapping the 4l80e tune from a 2500 HD, I didn't do the tire/gear wizard change with what my truck actually has which resulted in the "trans revolutions/mile" (Speedo>Calibration>Gear Ratio&size) being the wrong value. Once changing the gear/tire wizard on the tune I took the segment swap from it gave me a different value for the revolution/mile than what I had; changing this to the correct value made all my issues go away.