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Thread: Cos5 help after loading tune car wont start without maf plugged in

  1. #1
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    Default Cos5 help after loading tune car wont start without maf plugged in

    I switched to cos5 to go speed density. But with a smooth hose in place of the maf the car wont crank until the maf fails.sometimes 50 cranks to fo it which will kill a battery.
    I have to do all tuning with maf in line then crank it. Once it fails the maf it will crank fine without the maf but its not convenient.
    Any suggestions?
    2000 NBM trans am.
    427 Dart ship block,Lme ported Ls7 heads 12.5 compression
    246/262 .730/.712 112+4 low lash solid roller
    Rmvb 4l80 with transbrake, 8" FTI converter
    12 bolt Moser rear end with 4.10 gears

  2. #2
    Joe (Moderator) joecar's Avatar
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    Post your before/after tune files.

  3. #3
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    Joe i wish i could. I'm on a boat until next Tuesday. I have the lap top but can not post from it. Only from my phone.
    Even Geoff at engine power systems who was helping me was baffled. Never had 1 do this going cos5
    2000 NBM trans am.
    427 Dart ship block,Lme ported Ls7 heads 12.5 compression
    246/262 .730/.712 112+4 low lash solid roller
    Rmvb 4l80 with transbrake, 8" FTI converter
    12 bolt Moser rear end with 4.10 gears

  4. #4
    Joe (Moderator) joecar's Avatar
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    Check that table B3647 has been correctly populated (because it will contain data from the previous OEM table B3605 which has a different axis)...

    B3605 is ECT x MAP <--- previous tune
    B3647 is RPM x MAP <--- new tune (COS)

    the cold ECT data will show up as low RPM data, this is way to rich for the engine to run.

  5. #5
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    All set at 1.0 in 3647 until 95 and 100 kpa
    2000 NBM trans am.
    427 Dart ship block,Lme ported Ls7 heads 12.5 compression
    246/262 .730/.712 112+4 low lash solid roller
    Rmvb 4l80 with transbrake, 8" FTI converter
    12 bolt Moser rear end with 4.10 gears

  6. #6
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    2000 NBM trans am.
    427 Dart ship block,Lme ported Ls7 heads 12.5 compression
    246/262 .730/.712 112+4 low lash solid roller
    Rmvb 4l80 with transbrake, 8" FTI converter
    12 bolt Moser rear end with 4.10 gears

  7. #7
    Joe (Moderator) joecar's Avatar
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    photobucket is not showing your pic.

  8. #8
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    I sent it in pm
    2000 NBM trans am.
    427 Dart ship block,Lme ported Ls7 heads 12.5 compression
    246/262 .730/.712 112+4 low lash solid roller
    Rmvb 4l80 with transbrake, 8" FTI converter
    12 bolt Moser rear end with 4.10 gears

  9. #9
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    I fixed the issue. First cell in maf calibration set to 15 so it would provide enough fuel to start. Work's great now
    2000 NBM trans am.
    427 Dart ship block,Lme ported Ls7 heads 12.5 compression
    246/262 .730/.712 112+4 low lash solid roller
    Rmvb 4l80 with transbrake, 8" FTI converter
    12 bolt Moser rear end with 4.10 gears

  10. #10
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by Aint Skeered View Post
    I fixed the issue. First cell in maf calibration set to 15 so it would provide enough fuel to start. Work's great now
    That's because in some cases the PCM doesn't fail the MAF immediately...

    good fix, I saw that on LS1tech yesterday and I was trying to locate this thread... thanks for updating.

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