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1997 5.7 l chevy z71 power problems

Discussion in 'Engine Performance + Maintenance' started by bosox91379, Jan 29, 2011.

  1. bosox91379

    bosox91379 Newbie

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    Jan 29, 2011
    I have a 97 chevy with a 5.7L that seems to lose power on the highway. I have changed all the usual stuff. plugs, wires, and the cap and rotor. I changed the oil also. It seems that this truck would haul ass but it wants to down shift while passig all the time and seems to struggle at highway speeds. I would like it to run like a champ when I haul my boat any suggestions would be awesome!
  2. RHamill

    RHamill Ryan

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    Nov 4, 2010
    The 26th State
    What gears? If you don't know, open glove box, the RPO codes are in alphabetical order, GT4 is 3.73(s) and GU6 is 3.42(s) - the (s) is there because of the 4x2 and 4x4 differences.

    Maybe get some spray seafoam with the long straw, and being a vortec engine, just pouring it in the vacuum hose off the intake will only get the rear four cylinders. If you get the spray stuff with the straw, run the truck for 5-10 mins, take off air intake from throttle body, put the straw all the way back way past throttle plate and start spraying and gradually pull it out. Let it soak for 5-10 mins then run your truck, rev it a few times then drive it kind of hard but not reckless until all the smoke clears, the smoke is from carbon build up in cylinders and what not, it made a small difference in revs and acceleration for my 96 5.7l.

    I thought maybe the smoke was a little show seafoam makes your truck do to make you believe it works, so I did it again, and the smoke was WAAY less than before.

    Did you gap the plugs to .060?

    What size tires? that can interfere with shifting if you are running stock gears with big tires.
  3. Mike

    Mike Administrator Deluxe Staff Member

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    Dec 2, 2009
    Check for vacuum leaks or a bad fuel pump and also do your fuel filter.
  4. silverado13

    silverado13 GEAR HEAD

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    Mar 4, 2011
    Baton Rouge Louisiana
    ive heard of cat converters doing this

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