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MPG is dropping - advice?

Discussion in '1st Gen. Tacomas (1995-2004)' started by Tenalquot, Nov 25, 2009.

  1. Nov 25, 2009 at 9:43 PM
    #1
    Tenalquot

    Tenalquot [OP] Member

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    Hi All,

    My Tacoma has always delivered at least 26mpg highway when not hauling. I tune it religiously and it has never given me a bit of trouble.

    About two months ago I got a check engine light. I cleared the light and it came right back so I had it checked by two seperate shops- I needed a new Throttle Position Sensor.

    I changed out the OEM part for an aftermarket replacement from Autozone and that's when the drop in MPG happened. Now I get 22-23mpg hwy. It seems to run just like before, except for the low mpgs.

    Anyone else had this problem? Do I need to bite it and buy the OEM part?

    What else should I check besides this?

    Vital stats:

    '99 2.4l 2wd with 190k on the clock. I run medium grade gas.
     
  2. Nov 25, 2009 at 9:50 PM
    #2
    FuTang909Inamo

    FuTang909Inamo Well-Known Member

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    Might be because of "winter gas".
     
  3. Nov 25, 2009 at 9:53 PM
    #3
    Tenalquot

    Tenalquot [OP] Member

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    It's never happened in past years. Unless there's a new extra crappy formula this year?
     
  4. Nov 25, 2009 at 9:59 PM
    #4
    FuTang909Inamo

    FuTang909Inamo Well-Known Member

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    Not sure bro...you tune it regularly...no other codes? The only variable that I see is the one you pointed out "Autozone" .
     
  5. Nov 25, 2009 at 10:04 PM
    #5
    dwalden2

    dwalden2 Your mom goes to college

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    Since they've switched to "winter gas", mine's dropped anywhere from 1-2 mpg. That might be all it is. If you don't have any other problems and got the TPS fixed and keep it tuned, I don't see anything else that would be the problem.
     
  6. Nov 26, 2009 at 7:07 AM
    #6
    blackxpress

    blackxpress Well-Known Member

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    Hey, dwalden2. I see you're from Blue Ridge. My mom lives in Blairsville. i did too until I moved up here to Buckeye land 2 yrs ago.

    Anyway, back to the original thread: I would suspect that Autozone TPS. I don't know this for sure but I think the TPS can be off a little and still not set a code as long as it's within an acceptable range. It could be throwing your injector timing off just enough to effect your fuel mileage without being off enough to turn on the CEL.
     
  7. Nov 26, 2009 at 9:44 PM
    #7
    Tenalquot

    Tenalquot [OP] Member

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    It smells like the TPS to me too. I wish I could try out an OEM unit for a week before I shell out the scratch.

    I guess I'll just have to quit being such a cheapskate.
     
  8. Nov 26, 2009 at 10:06 PM
    #8
    WhatThePho?

    WhatThePho? Greg Graffin 2016

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    How much percent Ethanol is in the gas at your local station? Around here if I find or can find any station with no Ethanol in the gas I get 1-2 mpg better, but now all the pumps I see have 10 - 15 % ethanol in them.
     
  9. Nov 26, 2009 at 10:08 PM
    #9
    tacomaman06

    tacomaman06 Carolina Alliance: Enforcer

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    getting there....
    im gonna guess its the aftermarket tps thats the culprit. ive seen quite a few times when folks have replaced things like that and o2 sensors with aftermarkets, and had problems............may be a lil more, but sticking with oem on stuff like that is better in the long run.
     
  10. Nov 26, 2009 at 10:12 PM
    #10
    dwalden2

    dwalden2 Your mom goes to college

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    Yes sir. I love it here...even if driving up and down the hills/mountains gives me lower mileage than most people on this site. During the winter I get about 14-15 consistently, unless I drive down to Kennesaw/ATL...then I get around 16-17 with "winter gas".

    Blarisville's gettin bigger...they got a Wal-Mart! haha.
     
  11. Nov 26, 2009 at 11:00 PM
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    Tenalquot

    Tenalquot [OP] Member

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    I don't know, but it hasn't affected my mileage this much in past years.

    Friggin aftermarket crap. But I couldn't get an OEM TPS here except by mail and I couldn't wait.

    That'll learn me.
     
  12. Nov 27, 2009 at 12:52 PM
    #12
    blackxpress

    blackxpress Well-Known Member

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    Good think you've got the offroad package. Fannin County has some of the worst roads in the country.
     
  13. Dec 1, 2009 at 6:06 PM
    #13
    Tenalquot

    Tenalquot [OP] Member

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    Update

    To test the "winter gas" theory I switched to premium- bingo. I'm back up to 26mpg on the highway.

    I don't know what they did to the medium-grade 89 octane I usually run, but it never affected my '99 this bad in past years.

    Ill be using the expensive stuff at least until spring.
     
  14. Dec 1, 2009 at 6:26 PM
    #14
    Kenobe

    Kenobe Well-Known Member

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    Did you re-air your tires? You do know to swap out winter and summer air in your tires, right?










    :D
     
  15. Dec 1, 2009 at 6:51 PM
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    pittim

    pittim mittip

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    Pink slider.
    I got 14mpg last time I filled up.

    :/
     
  16. Dec 2, 2009 at 12:55 AM
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    WhatThePho?

    WhatThePho? Greg Graffin 2016

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    I'm right around there and that's adding 6% for the revolution difference for the 33's
     
  17. Dec 2, 2009 at 9:21 AM
    #17
    Tenalquot

    Tenalquot [OP] Member

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    Yup. I also changed the oil from Wesson to Olive to cut down on arterial buildup.
     
  18. Dec 2, 2009 at 9:38 AM
    #18
    pittim

    pittim mittip

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    I think my low (young) age has something to do with the low mpg I've been getting :anonymous:
     
  19. Dec 2, 2009 at 10:25 AM
    #19
    brg88tx

    brg88tx Well-Known Member

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    i've been getting an average of 19.83 mpg with my 2003 prerunner v6 so far in my first month of ownership.
     
  20. Dec 2, 2009 at 5:03 PM
    #20
    Tenalquot

    Tenalquot [OP] Member

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    Mine's a 2wd 4 cyl. It's great to own a truck that I can also commute in!
     
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