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Thread: 2009 Z06 E38 Runaway throttle with AC on only but AC torque compensation is off!

  1. #1
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    Default 2009 Z06 E38 Runaway throttle with AC on only but AC torque compensation is off!

    The car is highly modified and has a Harrop Hurricane ITB manifold. I have both B1825 and B1826 AC torque compensation set to zero however the car occasionally accelerates on its own with the AC on when starting off from a stop. Also again only with the AC on at idle if I rev the engine the throttle will stick at various RPM. On the road only with AC on under cruising conditions at 1800 RPM the throttle will hold at 1800 kind of like the cruise control is on. In all situations when the AC is switched off the problem immediately stops. I have also significantly reduced B2804 Throttle Open Rate Limits as shown below.

    30.000305 30.000305 30.000305 30.000305 30.000305 30.000305 30.000305 30.000305
    39.999389 39.999389 39.999389 39.999389 39.999389 39.999389 39.999389 39.999389
    50.000000 50.000000 50.000000 50.000000 50.000000 50.000000 50.000000 50.000000
    60.000610 60.000610 60.000610 60.000610 60.000610 60.000610 60.000610 60.000610
    69.999695 69.999695 69.999695 69.999695 69.999695 69.999695 69.999695 69.999695

    This seems to have helped the problem some along with the AC torques compensation, it used to accelerate out of control to the rev limiter and now it just accelerates a little bit or holds the RPM. Does anyone know if there is another table that is controlling the throttle when the AC is turned on? Also how far down can I go on the Throttle Open Rate Limits. I have been reducing down from 99.99 10 points at a time I am wondering if I can go negative. It seems that I may have already gone as far as it can go as the last couple of reductions seemed to have no noticeable difference.

    Lastly this reduction in the Throttle Open Rate limits has made the cruise control almost usable. Before with the cruise on the car would buck and surge as the throttle adjustments made by the cruise were so large that it was unusable. Now it is just a little irritating. I plan to make some more dramatic reductions in the table to see if it gets better.

  2. #2
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    You can go down to single digits in the rate table. That will significantly soften the open rates. Never tried zero.

  3. #3
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    Default 2009 Z06 E38 Runaway throttle with AC on only but AC torque compensation is off!

    sounds like idle air g/s is to high

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    Quote Originally Posted by turbo View Post
    sounds like idle air g/s is to high
    What is idle air g/s. I looked around under idle but could not find a table that matched that.

  5. #5
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    Default 2009 Z06 E38 Runaway throttle with AC on only but AC torque compensation is off!

    B1829. can do what you are saying if it has been set to high

  6. #6
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    Quote Originally Posted by turbo View Post
    B1829. can do what you are saying if it has been set to high
    B1829 Minimum Idle Airflow is set to zero from 1200 RPM on up to 8000. From 250 to 1000 RPM it looks like this.

    250 - 2.3242
    450 - 2.3242
    650 - 2.3242
    800 - 2.4609
    1000 - 1.4766
    1200 and up is all zeros. All settings the same for all gears. I am not sure how all zeros above 1000 could make it accelerate or stick but I am open to ideas.

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