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Very Poor Fuel Mileage on 2003 Silverado

Discussion in 'Performance & Fuel' started by zachh1020, Jan 24, 2012.

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  1. zachh1020

    zachh1020 Rockstar 100 Posts

    Hi All,

    I have a 2003 Silverado 1500 4.8L.

    Over the last week or so, I've gone from around 14MPG Average to 2-3MPG Average!

    Exhaust smells strong of gasoline. Poor Power.

    What are the first things I need to start checking? Injector stuck open? Not sure.


    99'HEARTBEAT Epic Member Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    I would First have the Truck Scanned to see if it has any Trouble Codes.......and have you done any maintenance lately??
  3. zachh1020

    zachh1020 Rockstar 100 Posts

    The first thing I did was scan it. Not throwing up any codes. Nothing done lately. Oil Change about 1 - 1 1/2 months ago. I even verified the MPG on a secondary device plugged into my OBD. Shows the same.

    99'HEARTBEAT Epic Member Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    With no codes coming-up, you could look at doing some of the following,
    Check the Fuel Pressure
    .......New Fuel Filer
    ......A Cleaning of the Throttle Body and Injector's

  5. vncj96

    vncj96 Epic Member 5+ Years 1000 Posts

    i am surprised the truck will even run, as it would seem apperant that it is running extremely rich. thus I am suprised the plugs are even able to fire as the cylinder must be getting way to much fuel to burn off thus the strong smell of gas. Fuel injectors could be malfunctioning or are jus flowing fuel instead of spraying it as they should. And to not have a code seems weird as well. Is the engine stumbling or choking out? Black smoke out the tailpipe when you rev the gas up? It could be the mass airflow sensor as well as if it has malfunctioned and is reading alot of air flow it will dump in more fuel as well....
  6. Jim Jordan

    Jim Jordan New Member

    I noticed a dramatic drop in mpg of my 2003 Silverado 5.3 2wd as well recently. Did you find out the problem??
  7. Jim Jordan

    Jim Jordan New Member

    FYI, I had my transmission serviced, and my mileage has returned to normal levels.....

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