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Thread: Decel fuel off

  1. #1
    Join Date
    Dec 2017
    Posts
    11

    Default Decel fuel off

    My msd atomic is installed on a stock LS1 with an ls6 intake. Itís running really well except the fuel ratio leans on every time you take your foot off the accelerator. It gets really bad if you come from higher speeds to a stop.

    Does anyone know how to turn the decel fuel to on?


    Thanks
    Steve

  2. #2
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    919

    Default

    Hi Steve,

    Are you running an air/oil separator, since no fuel on decel should not produce hydrocarbons on decel, like all cars do.
    Perhaps oil in the pcv on high manifold vacuum is the slow or abnormal combustion that produces the high hydrocarbon reading on closed throttle.

    Gary
    Regards

    Gary

  3. #3
    Join Date
    Dec 2017
    Posts
    11

    Default

    The machine and monitors showed the air fuel ratio shooting to around 20:1 before the HC spike.
    As soon as you crack the throttle open or come back onto the accelerator the fuel ratio corrects itself and the HC goes back down immediately.

    I've written to MSD twice asking them for help on how to effect the MAP settings or just getting the fuel decel turned on, which you would think would be an easy fix.

    I'm not sure what else to do.

    Their product support and general communication are terrible.
    Im thinking I will just have to replace it with something else - probably just the stock loom and ecu.
    I wont be recommending MSD products to anyone after my experiences.

  4. #4
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    919

    Default

    Hello again Steve,

    Just reading on here page 21, shows whether decel fuel is active?
    https://www.jegs.com/InstallationIns...1/121-2958.pdf

    Gary
    Regards

    Gary

  5. #5
    Join Date
    Dec 2017
    Posts
    11

    Default

    G'day Gary,
    The decel fuel is off regardless of engine temp or whether learning.

    I rang MSD during their office hours. They said you cant turn it on with the hand held.
    They are much more helpful on the phone.

    They told me to connect the speed sensor wires (lt blue and brown) to the gearbox as it can help with transitioning smoother back to idle.
    I've connected them up to the gearbox vehicle speed sensor. I hope they are the right way round.
    It doesn't drive any differently.

    I also spent a bit of time getting the IAC setting spot on 20.


    I guess I'll have to get it checked again and see how it goes.

  6. #6
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    919

    Default

    Yes, I guess if it has that capability to look at vehicle speed, then it would run similar to when VSS signal is lost in factory ECM vehicles. Holden 5.0 in VS is a good example.
    Gary
    Regards

    Gary

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