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Thread: LTFT running rich

  1. #1
    Potential Tuner Rano90's Avatar
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    LTFT running rich

    I just got my MPVI and started a log on my 2014 Yukon Denali. I noticed it was running rich most of the time LTFT reaching -17.
    I added my log here..can anyone advise me what I need to be looking at first?
    is it bad O2 sensors or should I go ahead and do a MAS re-calibration.
    Appreciate the support.

    the car is in stock form fully, except for a muffler delete.

    GMC-YukonDenali2014 - Cruise After base tune2.hpl

    and this is the current tune on the car
    GMC-YukonDenali2014 - Tourque Converter Slip.hpt

    And here is the first log I took at stock ECU tune
    GMC-YukonDenali2014 - Base Drive.hpl
    Last edited by Rano90; 4 Weeks Ago at 11:50 PM.

  2. #2
    Senior Tuner edcmat-l1's Avatar
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    What's done to the vehicle? Or are we playing a guessing game?

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  3. #3
    Potential Tuner Rano90's Avatar
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    Quote Originally Posted by edcmat-l1 View Post
    What's done to the vehicle? Or are we playing a guessing game?
    the car is in stock form fully, except for a muffler delete.

  4. #4
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    Looks Ok to me.. Even stock cars aren't 0/0.

    Tune away.. Specifically the MAF table would be a good start.
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  5. #5
    Potential Tuner Rano90's Avatar
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    Quote Originally Posted by Alvin View Post
    Looks Ok to me.. Even stock cars aren't 0/0.

    Tune away.. Specifically the MAF table would be a good start.
    So I shouldn't be worried about the -17 values? I got these even after resetting the LTFTs.

    Thanks for the reply.

  6. #6
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    Is it Flex Fuel?

  7. #7
    Senior Tuner edcmat-l1's Avatar
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    It's better running in the negatives than positive. If it were adding fuel that would be a sign of lower fuel pressure.

    Being off 17% is nothing to worry about. It has to be off a lot more than that before the PCM thinks somethings wrong.

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  8. #8
    Potential Tuner Rano90's Avatar
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    Quote Originally Posted by 2xLS1 View Post
    Is it Flex Fuel?
    No, gasoline

  9. #9
    Tuning Addict blindsquirrel's Avatar
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    By not posting the tune file you're forcing people to ask things, and those are things you may not fully understand, and so the questions have to be asked multiple times before the real information gets transmitted. But if you post the tune file, we can open it and see if Virtual Flex is still enabled, and then tell you to turn that off and never turn it on again.
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  10. #10
    Potential Tuner Rano90's Avatar
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    Quote Originally Posted by blindsquirrel View Post
    By not posting the tune file you're forcing people to ask things, and those are things you may not fully understand, and so the questions have to be asked multiple times before the real information gets transmitted. But if you post the tune file, we can open it and see if Virtual Flex is still enabled, and then tell you to turn that off and never turn it on again.
    Thank you for the response...It's my first time here, appreciate it. This is the current tune on the car.

    GMC-YukonDenali2014 - Tourque Converter Slip.hpt

  11. #11
    Potential Tuner Rano90's Avatar
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    Quote Originally Posted by edcmat-l1 View Post
    It's better running in the negatives than positive. If it were adding fuel that would be a sign of lower fuel pressure.

    Being off 17% is nothing to worry about. It has to be off a lot more than that before the PCM thinks somethings wrong.
    Thank you so much, appreciate the advice.

  12. #12
    Tuning Addict blindsquirrel's Avatar
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    Stock except muffler delete and DOD disabled and idle speed adjusted and virtual flex turned off and lots of transmission changes and also some other stuff, is different from a flat statement of 'stock except muffler delete'.
    GM Gen4 Injectors v2.1.xls
    ChatGPT is the end result of someone assuming that if they gather up a large enough pile of sh*t it will spontaneously generate a pony.

  13. #13
    Potential Tuner Rano90's Avatar
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    Quote Originally Posted by blindsquirrel View Post
    Stock except muffler delete and DOD disabled and idle speed adjusted and virtual flex turned off and lots of transmission changes and also some other stuff, is different from a flat statement of 'stock except muffler delete'.
    Apologies for that, I thought these should not be affecting fueling, As I've seen LTFTs at -17 even with the first drive log I took with stock ECU tune. I'm attaching that log hereGMC-YukonDenali2014 - Base Drive.hpl