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Thread: Super lean, off idle stumble.

  1. #1

    Default Super lean, off idle stumble.

    Having an issue where the AFR goes super lean at low throttle angle and low RPM. I've tried Acceleration Enrichment, but it doesn't help in this area. I found the Injector End Angle at 90° and changed that to 0°, which made a small improvement. I adjusted the fuel map to have more resolution, however, it doen't seem to make a difference. I've tried Blanking at 4 & 1 with no perceptible difference. I checked the pedal map and it's accurate. I added some timing (maybe too much?) and didn't seem to help. Higher rpm or throttle angle seem to be fine. I've attached several datalogs that show the issue very clearly. Engine is an LS7 with ProCharger. Cam is 287°/301° duration with .600" lift. Global and

  2. #2
    Join Date
    May 2014
    Bostwick, GA


    Just looked at your tune.
    I see that you have Closed Loop at 50%
    Idle AFR at 14.5. I doubt that engine will idle well at that AFR. Maybe mid/high 13s?
    Ignition Parameters set to custom? What are you using?
    1 knock sensor?
    Looks like the fuel graph has a big hole in it around the idle area.
    Acceleration Enrichment table appears to need work.
    Just some amatuer observations. Hopefully, the pros will be along shortly!
    Last edited by Chuck L.; 07-13-2021 at 09:53 AM.

  3. #3


    With the low level of vacuum at idle, you might consider tuning in Combo mode (Alpha-N & VE). Also, the load axes for the Base Fuel & Spark Tables don't match. Unless this is a dedicated race car, you have way too much resolution for boost and not enough in the NA area. Andrew
    Instagram: @projectgattago
    Offering remote Holley EFI tuning.
    I deliver what EFI promises.
    Please get in touch if I can be of service.

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