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Thread: Interesting Issue: MAF failure = Idle tables ignored. Cant tune VE because of it

  1. #1
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    Default Interesting Issue: MAF failure = Idle tables ignored. Cant tune VE because of it

    So im working on my 2007 Silverado with a 4.8 and ran into something interesting.

    I put a 224/230 .553/.546 111+2 Cam, bolt ons, stall, various stuff in the last week.


    What i found is when i cause the maf to fail by reversing the values in c0301 and c0302 (So i could dial in the V VE tables), the ecm completely ignored what seems like all the idle tables. It attempted to idle at 500 rpm with 28 degrees on timing. I did everything... changing the idle airflow, max idle area, and idle set points all over with no change in the way the engine tried to idle.

    After a lot of searching i found a obscure post about a similar issue stating on some e38's... the ecm ignores the idle tables when a map/maf failure is detected. So.....

    I put the maf settings back so it would not fail... and boom... it instantly idled and appears to respond to my changes in the idle tables.

    So if i cant fail the MAF.... how am I supposed to log and tune in SD to get my VE dialed in?

    I appreciate any help. TIA

  2. #2
    Joe (Moderator) joecar's Avatar
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    When the ECM ignores idle tables on MAF fail, which tables is it using...?

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    it is worth pushing your VVE table up and down. For example try 15% up and see if it gets better. SD MAF on scan should match Real MAF. Roughly that is. If your setup has moved the airflow away from stock too far, yes idling may be a challenge.

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    Quote Originally Posted by joecar View Post
    When the ECM ignores idle tables on MAF fail, which tables is it using...?
    It uses the high octane spark table rather than the idle spark. B1829, B1821, b1651, b1652, all what seems like all the idle tables are not referenced Whatsoever. You can change the values to whatever you want and log it.... it will act exactly the same. Tries to idle at 500 rpm using the high octane spark table. Its like the ecm loses its mind without the maf. Really frustrating.

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    Quote Originally Posted by gmh308 View Post
    it is worth pushing your VVE table up and down. For example try 15% up and see if it gets better. SD MAF on scan should match Real MAF. Roughly that is. If your setup has moved the airflow away from stock too far, yes idling may be a challenge.
    Have tried this with no luck unfortunately. Im nearly positive it is not referencing the idle tables.

  6. #6
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    Can you post your tune file?

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