getting 8.5 mpg need help

Discussion in 'Engine & Drivetrain' started by BlueCollarTahoe, Apr 9, 2018.

  1. afpj

    afpj Full Access Member

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    The fuel trims you posted look OK. If you had a vacuum leak would expect them to be a bit off at idle. Someone mentioned it earlier but did you clean the maf and throttlebody? Check your brakes for evidence of dragging? Perhaps lift up the rear and turn the wheels to make sure the parking brake is not dragging as well? Just mentioning the simple stuff that I am capable of. I’m not a sophisticated type of dude, and I apologize if you’ve already checked those.
     
  2. bottomline2000

    bottomline2000 Full Access Member

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    I was just about to mention this. If you have an infrared temp gun I would check the temp of each rotor after driving and see if one or more were excessively hot. (Harbor freight has one for a decent price, less than $20. I checked it against my digital thermostats in the house and its fairly accurate.) I did this after a major brake job and they were all fairly consistent in temp front to back around 80-100 deg but I have aftermarket drilled/slottted rotors but you get the idea.

    Sent from my SAMSUNG-SM-T377A using Tapatalk
     
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  3. swathdiver

    swathdiver Full Access Member

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    What is normal throttle plate percentage for GMT800? If that were a GMT900 that would be considered a little high and recommend to be cleaned. Mine was 7-8% during my tune and we cleaned it afterwards and it was down to 3-5%.

    The snapshot of the trims doesn't really tell us much other than that they look ok. A snapshot over time would be better.

    http://www.tahoeyukonforum.com/threads/fuel-trims-crazy.101453/
     
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  4. BlueCollarTahoe

    BlueCollarTahoe Full Access Member

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    im gonna have them checked monday i replaced one caliper maybe a year ago and crazy enough this morning i got the scratching noise you get when the pads ar elow. these are relatively new Wagner pads. less than 10k miles on them. im starting to think the caliper they put on was put on wrong the whole time or something either way im gonna look at this. my ebrake things are rusted to hell but they still work lol and never apologize i appricate all of yall taking the time to help me out.



    love harbor freight lol whats the proper temp? or jus tlook for one or two thats way off?


    okay ill clean everything out again. the fuel trims over time i dont understand. should i record at idle and then whats the next interval? i can do it today
     
  5. BlueCollarTahoe

    BlueCollarTahoe Full Access Member

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    also can a weak battery have influence on MPG?
     
  6. swathdiver

    swathdiver Full Access Member

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    Ideally, your Long Term trims should be at or near zero all the time. If something is wrong, like an intake manifold leak for example, the LT trims will be in the high teens or greater at idle and come down while driving. Exhaust leaks can also skew the numbers.

    Go for a drive and record, idle in park, in drive idling and then go for a short drive and womp on it if you can a time or two and then play it back when you get her home.

    As for the battery IDK.
     
    Last edited: Apr 14, 2018
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  7. bottomline2000

    bottomline2000 Full Access Member

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    Yes it can, but usually your alternator powers the vehicle while its to running. If it were bad you would see a batt light more than likely.

    And yes, look for a wheel/s that is a lot higher in temp than the others.

    Sent from my SAMSUNG-SM-T377A using Tapatalk
     
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  8. mudpup

    mudpup TYF Newbie

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    Try cleaning your mass air flow sensor, it helped on my 96 tahoe with the same problem.
     
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  9. prrowe00

    prrowe00 TYF Newbie

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    Did your say you got something reprogrammed? If yes
    Check if you odemeter is reading a mile as a mile, test on interstate between mile markers or gps a location and compare actual mileage to google.
    I had a truck once that the dash went out on and the new one was programmed for Kilometers.
     
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  10. HiHoeSilver

    HiHoeSilver Away! Supporting Member

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    I second this. A dirty MAF can screw you up. Also, a can of Kreen through the top end never hurts.
     
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