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    punchy's Avatar
    punchy Posts: 1, Reputation: 1
    New Member
    		  
    #1

    Dec 3, 2007, 11:20 AM
    1991 GMC Gas Mileage
    I have a 1991 3/4 ton 4WD GMC sierra (bare bones truck, no air, no cruise, no power anything, 5.0 liter throttle body EFI.
    This truck seems to drink gas with a voracious appetite.

    Does anyone know of a common problem that could be causing such bad milage?
    I feel like it's getting in the 6-8 mpg range.

    Someone mentioned to me that the throttle body gasket could be leaking,
    It does run rough until it warms up for about 5-10 minutes.

    It does not leak any gas while setting, I've checked.
    Thanks for any info,

    Andy
    CaptainRich's Avatar
    CaptainRich Posts: 4,492, Reputation: 537
    Cars & Trucks Expert
    		  
    #2

    Dec 3, 2007, 11:29 AM
    Quote Originally Posted by punchy
    I have a 1991 3/4 ton 4WD GMC sierra (bare bones truck, no air, no cruise, no power anything, 5.0 liter throttle body EFI.
    This truck seems to drink gas with a voracious appetite.

    Does anyone know of a common problem that could be causing such bad milage?
    I feel like it's getting in the 6-8 mpg range.

    Someone mentioned to me that the throttle body gasket could be leaking,
    It does run rough until it warms up for about 5-10 minutes.

    It does not leak any gas while setting, I've checked.
    Thanks for any info,

    Andy
    That engine/truck combo never got real good mileage.
    The type and size of tires can have dramatic effects on fuel consumption, as well.
    Inspect the throttlebody by first removing the aircleaner cover and while holding the throttle open shine a light down into the open bore, looking for pieces of gasket stick out. Also when was the last time it had a complete secondary ignition update? Or a fresh fuel filter?
    You may also be a victim of "winter blend" fuel, available in some areas.
    TxGreaseMonkey's Avatar
    TxGreaseMonkey Posts: 16,761, Reputation: 5597
    Uber Member
    		  
    #3

    Dec 3, 2007, 11:59 AM
    Go over your ignition system. Consider replacing spark plugs (ACDelco only), spark plug wires, rotor, and distributor cap. A failing oxygen sensor or clogged air filter can also waste a lot of gas. Check the link below for other tips:

    https://www.askmehelpdesk.com/cars-t...tml#post293582
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