Thread: Swapped PCM leading to low LTFT and idk why!?

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  1. #1 Swapped PCM leading to low LTFT and idk why!? 
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    Okay so I have a 2008 Grand Prix which, for some reason, isn't compatible with HP Tuners. To get around this I sapped out my 2008 PCU with one from a 2006 but even since I did the scanner is reading really low fuel trims when I'm at or near idle and I don't know why. I can't figure out for the life of me what is different between the 2006 and 2008 that would cause this??? Please help!Swapped PCM leading to low LTFT and idk why!?-capture-jpg
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  2. #2 Re: Swapped PCM leading to low LTFT and idk why!? 
    Killa Bee Scottydoggs's Avatar
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    have you checked if your maf is the same part number as the year of the pcm? might just need the maf turned up.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  3. #3 Re: Swapped PCM leading to low LTFT and idk why!? 
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    I think so but how can I check?
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  4. #4 Re: Swapped PCM leading to low LTFT and idk why!? 
    Killa Bee Scottydoggs's Avatar
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    go to rock auto and search for a maf for your car and the donor pcm's car and see if the part # is different. if it is, thats the issue most likely.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  5. #5 Re: Swapped PCM leading to low LTFT and idk why!? 
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    Yeah they're both the same
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  6. #6 Re: Swapped PCM leading to low LTFT and idk why!? 
    Killa Bee Scottydoggs's Avatar
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    you can take some fuel from the maf. just a little bit in the lower areas, 1000-3000 is idle range, 3-7000 is cruise, 7 to the top is wot.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  7. #7 Re: Swapped PCM leading to low LTFT and idk why!? 
    Turbo is the way to go. BillBoost37's Avatar
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    Have you compared the two bins for fueling and airflow? GM changed some stuff from year to year and if you look..likely you can find it and copy the table in.
    I drink..so consider that when reading my posts.

    2010 Audi A6 Dual IC's
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  8. #8 Re: Swapped PCM leading to low LTFT and idk why!? 
    Turbo is the way to go. Fivefingerdeathpunch's Avatar
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    2008 was a year only computer/calibration as they started the switch to can-bus, that is why it was never supported. Not worth their time to make a editable file for 1 year.

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  9. #9 Re: Swapped PCM leading to low LTFT and idk why!? 
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    What does that mean?
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  10. #10 Re: Swapped PCM leading to low LTFT and idk why!? 
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    That's what I was thinking but I don't know where to find a stock tune file for a 2008.
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  11. #11 Re: Swapped PCM leading to low LTFT and idk why!? 
    Killa Bee Scottydoggs's Avatar
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    its time tp learn maf tuning

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  12. #12 Re: Swapped PCM leading to low LTFT and idk why!? 
    Turbo is the way to go. Fivefingerdeathpunch's Avatar
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    There are no 2008 V6 stock files, nobody ever created one.

    DHP and HPT never supported that year so nothing is available.

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  13. #13 Re: Swapped PCM leading to low LTFT and idk why!? 
    GrandPrix Junkie SgtMarshal's Avatar
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    should have bought a GXP
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  14. #14 Re: Swapped PCM leading to low LTFT and idk why!? 
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    Okay I tried tuning the MAF table and it looks like that helped.
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  15. #15 Re: Swapped PCM leading to low LTFT and idk why!? 
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    So do you tune pcm looking to get mines done or order one from zzp got p0171 running lean stft is about 20.3 and ltft 16.3 Ik those aren't right no leaks changed fuel filter no luck
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  16. #16 Re: Swapped PCM leading to low LTFT and idk why!? 
    GT Level Member mguzzo's Avatar
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    Quote Originally Posted by 97gtp01gt99gt View Post
    So do you tune pcm looking to get mines done or order one from zzp got p0171 running lean stft is about 20.3 and ltft 16.3 Ik those aren't right no leaks changed fuel filter no luck
    with those lean trims, you probably have a vacuum leak. check again.
    --
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    Old '98 GTP Coupe: VS Cam, 3.0, S2IC, 42.5#, TOGs, N*/LQ4, Corsa. it once ran a 13 flat
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