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  1. #1
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    Default Bad gas mileage help

    Ive been having an issue with the mpg on my 05 grand prix base. Ive done plugs, wires lucas upper cylinder cleaner, sea foam cleaner for fuel lines ect. Cleaned the maf new air filter. Tire pressure is good and ive been driving pretty light footed for the most part. Any ideas

  2. #2
    GXP Level Member GTPpower's Avatar
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    Default Re: Bad gas mileage help

    Any cel's? How bad is bad?

    2001 GTP - cam, headers, nitrous, stock trans - 11.83 @ 116 <$2k in mods - sold
    2005 F350 6.0 - studded, deleted, bulletproofed, tuned
    1966 Olds Cutlass 442 Convertible
    2000 Chevy Silverado 2500 6.0l

  3. #3
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    Default Re: Bad gas mileage help

    No codes ..and like quarter tank in two days from back and forth from work ...where as before one tank would last pretty much 2 weeks and id drive on the weekend.

  4. #4
    GXP Level Member GTPpower's Avatar
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    Default Re: Bad gas mileage help

    You need to figure out what you are actually getting. That could be just a difference of how the fuel gauge reads or winter gas.

    2001 GTP - cam, headers, nitrous, stock trans - 11.83 @ 116 <$2k in mods - sold
    2005 F350 6.0 - studded, deleted, bulletproofed, tuned
    1966 Olds Cutlass 442 Convertible
    2000 Chevy Silverado 2500 6.0l

  5. #5
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    Default Re: Bad gas mileage help

    Question ...should my short term fuel trim be + all the time 0 and up while my long term is always -...like -15all the way to 25- and never going above from what ive seen so far on my odb reader

  6. #6
    GXP Level Member GTPpower's Avatar
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    Default Re: Bad gas mileage help

    It depends. But, I would look at your ltft. If it's 15-25 at cruise, you have some mechanical problems.

    2001 GTP - cam, headers, nitrous, stock trans - 11.83 @ 116 <$2k in mods - sold
    2005 F350 6.0 - studded, deleted, bulletproofed, tuned
    1966 Olds Cutlass 442 Convertible
    2000 Chevy Silverado 2500 6.0l

  7. #7
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    Default Re: Bad gas mileage help

    In the neg or pos?

  8. #8
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    Default Re: Bad gas mileage help

    I just replaced my thermostat. A 195 and on the reader it only shows it to reach 85 maybe my therm sensor? Is this related?

  9. #9
    GXP Level Member GTPpower's Avatar
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    Default Re: Bad gas mileage help

    Either negative or positive that far out is bad.

    Are you sure your reading in Fahrenheit and not Celsius?

    2001 GTP - cam, headers, nitrous, stock trans - 11.83 @ 116 <$2k in mods - sold
    2005 F350 6.0 - studded, deleted, bulletproofed, tuned
    1966 Olds Cutlass 442 Convertible
    2000 Chevy Silverado 2500 6.0l

  10. #10
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    Default Re: Bad gas mileage help

    In celsius. And with the values like that what would cause that? Probs a few different things

  11. #11
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    Default Re: Bad gas mileage help

    Temp wise on the dash it only gets to the 2 notch after the quarter mark

  12. #12
    GXP Level Member GTPpower's Avatar
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    Default Re: Bad gas mileage help

    85 Celsius is 185f. So you are not far off there.

    You could have a fuel issue or a sensor issue.

    2001 GTP - cam, headers, nitrous, stock trans - 11.83 @ 116 <$2k in mods - sold
    2005 F350 6.0 - studded, deleted, bulletproofed, tuned
    1966 Olds Cutlass 442 Convertible
    2000 Chevy Silverado 2500 6.0l

  13. #13
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    Default Re: Bad gas mileage help

    K well dont have a fuel pressure gage just yet...maybe look into the upstream 02 due to the negitive values or? Its just sucka because i have no codes and different possibilitys to check..just some ranging for low to high in cost

  14. #14
    GXP Level Member GTPpower's Avatar
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    Default Re: Bad gas mileage help

    An o2 would be a good guess, especially if it has 50k or more miles on it.

    2001 GTP - cam, headers, nitrous, stock trans - 11.83 @ 116 <$2k in mods - sold
    2005 F350 6.0 - studded, deleted, bulletproofed, tuned
    1966 Olds Cutlass 442 Convertible
    2000 Chevy Silverado 2500 6.0l

  15. #15
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    Default Re: Bad gas mileage help

    Okay so before i start changing things out...my short term is pretty much staying positve and my long term is always negative like -15 to-25ish.....o2 or maf?

  16. #16
    GXP Level Member GTPpower's Avatar
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    Default Re: Bad gas mileage help

    How many miles are on the o2?

    2001 GTP - cam, headers, nitrous, stock trans - 11.83 @ 116 <$2k in mods - sold
    2005 F350 6.0 - studded, deleted, bulletproofed, tuned
    1966 Olds Cutlass 442 Convertible
    2000 Chevy Silverado 2500 6.0l

  17. #17
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    Default Re: Bad gas mileage help

    Ive never changed in since we have had it around 07 08...yikes probs that? 170xxx on the od

  18. #18
    GXP Level Member GTPpower's Avatar
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    Default Re: Bad gas mileage help

    Put a new one in and just clean the maf.

    2001 GTP - cam, headers, nitrous, stock trans - 11.83 @ 116 <$2k in mods - sold
    2005 F350 6.0 - studded, deleted, bulletproofed, tuned
    1966 Olds Cutlass 442 Convertible
    2000 Chevy Silverado 2500 6.0l

  19. #19
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    Default Re: Bad gas mileage help

    Hey so after picking the o2 sensor up whats the socket size do i use

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