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  1. #1
    Join Date
    Jan 2011
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    Default 1997 5.7 l chevy z71 power problems

    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. #2
    Ryan RHamill's Avatar
    Join Date
    Nov 2010
    The 26th State
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    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.

    1996 Chevy K1500 "Old Red" [RIP] 9-10-12
    1998 Chevy K1500 - 5.7 Vortec - 4l60e - 3:73s - 6" RCX Lift - 3" PA Body Lift - TOWZ - 305/70r16 Goodyear Dura-Tracs - Black Housing Headlights - 16x10 American Eagle 186 wheels.
    ( oo == ss == oo )

  3. #3
    Administrator Deluxe Mike's Avatar
    Join Date
    Dec 2009
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    Check for vacuum leaks or a bad fuel pump and also do your fuel filter.

    MJ Engineering and Performance - 508.320.6807 - FB Page
    Professional 2-Way Tuning For Street, Race or Offroad

  4. #4
    GEAR HEAD silverado13's Avatar
    Join Date
    Mar 2011
    Baton Rouge Louisiana
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    ive heard of cat converters doing this

    -1997 k1500 ,ECSB, 350, built 4l60e with 2000 stall, air raid CAI, ported MAF sensor, ported throttle body, magnaflow catback with moroso spiral flow mufflers, flowtech shorty headers, escalade 3.73 rear end, underdrive crank pulley, overdrive alternator pulley, 411 swap with a custum tune, electric fan conversion, hypertech power programmer, viper push button starter, caddy cluster, 6000k HID hi/low conversion kit, blue interior LEDs-galore
    -2000 Silverado 1500 Z71 completely stock

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