Question about 1993 GMC Sierra

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78 GMC losing power

78 GMC High Sierra V8 350 has started to lose power everytime i go uphill or more than 40 mph and in highway, not sure why, i changed spark plugs, wires, oil, when i bought the truck it had new fuel pump, battery and starter, but air filter was missing, so i got a new one (truck purchased less than month ago) truck goes off when losing power but will start up again and run good on the street under 40mph

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  • Anonymous Feb 16, 2009

    I have the same problem but mine is a 2001 Buick Century

  • Angelo Attard
    Angelo Attard May 11, 2010

    sounds like a fuel problem have a look for any fuel filters may be one under truck as well

  • Anonymous Mar 16, 2014

    sluggish when pressing the accelerator but then runs good until you go uphill


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I had the same thing on a 73 vega yes a vega don,t laugh to hard it was a super car, it started not to go when I shifted gears and ask for more fuel I had a guy at the shell station look at it and replaced the fuel fliter, it worked,, maybe the pump was replaced but not the filter

Posted on Jan 08, 2009

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Check the fuel pump as well to see if you are getting the right amount of fuel if not the pump itself may run about 20 dollars or so , check timing as well just to see if your off if you have an advance on the distributor and if you go over 40 if it pops back up its the advance {had that problem once before }

Posted on Dec 30, 2008

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