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  1. #1

    Default Truck running lazy

    I have a 1999 GMC C2500. Put a new engine and got the truck running again. For some reason it feels like it has no power, gas milage is about 12-13 mpg. I have change spark plugs, wires and also done injector cleaner. Check fule pressure and stay right around 50 psi. No engine lights is on but the truck still feels lazy. oh, I also installed a new K&N cold air intake.

  2. #2
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    Default

    Quote Originally Posted by vieques View Post
    I have a 1999 GMC C2500. Put a new engine and got the truck running again. For some reason it feels like it has no power, gas milage is about 12-13 mpg. I have change spark plugs, wires and also done injector cleaner. Check fule pressure and stay right around 50 psi. No engine lights is on but the truck still feels lazy. oh, I also installed a new K&N cold air intake.
    could be fuel pressure is low. 5.7L you need 60 psi key on engine off. running should be 57 psi area.

    a restricted exhaust is another common power killer. with the 5.7L replacing the distributor is a good thing to do .

  3. #3

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    I checked the fule pressure the other day and with engine of was about 55 psi. I did not checked with the engine running. I will do that next. I have flow master muffler but still have the factory cat.

  4. #4
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    restricted exhaust can occur if the cat gets melted internally or the cat breaks apart and plugs up the muffler.

    remove the upstream O2 sensors . leave the holes open and see if power returns. if so then the exhaust is the problem.

    you saw 50 psi now 55 psi . this makes a big difference in engine power.50 is too low ..55 is good...

  5. #5

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    OkI will do that. i will keep you posted. Thanks.

  6. #6

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    If the truck has high milage & it hasn't been done already, you might want to replace the fuel filter also.
    You're driving is WAY more offensive than my swearing, assjack!!!


  7. #7
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    Quote Originally Posted by thrasher View Post
    If the truck has high milage & it hasn't been done already, you might want to replace the fuel filter also.
    good idea on the fuel filter .. a 2500 truck 12 MPG uses a lot of fuel so the filter need be replaced more often .

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