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Thread: twin turbo 5.3 - stall and lean spike on decel. Please Help!

  1. #1
    Tuner in Training
    Join Date
    Sep 2019
    Posts
    12

    twin turbo 5.3 - stall and lean spike on decel. Please Help!

    ive been fighting this for a while to no prevail..

    1968 Chevelle

    Twin 62mm L33 5.3
    SBE
    Pac 1218s
    decapped stock injectors at 69lb/hr - stock return style system at 58psi not boost referenced. unsure of fuel pump at this time but its not small.
    sloppy stage 2 cam (228/230)
    stock 4l80e / stock converter
    drive by wire TB from a 2004 chevy Van motor (or so im told)
    OLSD right now

    so im trying to tune VE with the owner of the car at the wheel, were just starting to get into some low boost (2psi) and ive discovered that it wants to go super lean on decel, and the throttle closes right up (sometimes TPS right down to zero very briefly) and stalls the car when decelerating to a stop. I believe i have DFCO completely disabled.

    The attached log doesnt show TPS to zero, but around 7% and super lean like 17-20:1 AFR.

    Could anybody help a guy out?

    dallas chevelle 05-25-20.hpl05-25-20 TT Chevelle Rev 6.hpt
    2009 - SRT8 Challenger 6 speed - Kenne Bell 2.8LC - 520whp (for now)
    2014 - Ram 1500 Sport
    2013 - Volkswagen Touareg 3.0 TDI
    2000 - Silverado 1500 - Turbo 5.3 - work In progress

  2. #2
    Advanced Tuner
    Join Date
    Feb 2015
    Location
    Perth, Australia
    Posts
    974
    Dfco must not be disabled correctly. You need to make sure you have it set to re re enable fuel on coast down before it wants to stall. Eg 1250rpm.

    If it’s disabled correctly you can tell by turning on stft and making sure the stft don’t go to zero on decel.

    If it all checks out then add some fuel in the VE table around vac areas like under 35kpa