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  1. #1
    Sr. Mechanic sc99z71's Avatar
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    Feb 2007
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    Moncks Corner, SC
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    Question Eingine "looping"

    Was wondering if anybody has this happen to their engine or has a clue of what might be causing it. At 45-55 mph with my foot slightly on the gas just to keep the speed constant, my engine will start to "loop" or somewhat sputter. But if it starts and I let off the gas or give it a little more gas it quits. At all other speeds this does not happen. And runs as smooth as a brand new engine otherwise. Any ideas????
    99 Silverado 1500 Z71
    5.3L 4L60E Tranny
    TransGo Shift Kit
    2.5" Rough Country
    Suspension Lift
    33" BF Good A/T
    Cherry Bomb Turbo
    Cobra CB w/
    Dual Fiberglass Antennas

    01 Kawasaki KLR650

  2. #2

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    Does the CEL/SES light come on? Can you see any smoke coming out the back?
    Scott

    ΜΟΛΩΝ ΛΑΒΕ

    '94 Chevy Suburban K1500
    3" exhaust w/ aero turbine non-baffled muffler
    CFM Technologies TB spacer
    CB w/ 44" whip antenna


  3. #3
    Sr. Mechanic sc99z71's Avatar
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    Default

    No light, no smoke, no nothing.....just annoying and I dont know if its doing anything to the engine.

  4. #4

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    Have you tried to duplicate the problem at other speeds, but the same RPM? For example, if you're normally at 2500 RPM @ 45 mph in 4th gear, have you tried to see if it happens at 2500 RPM in 2nd gear?

  5. #5
    Sr. Mechanic sc99z71's Avatar
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    Default

    I have not noticed it, but I will try it on the way home from work.

  6. #6

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    have you done any work to the truck mechanically recently?? say, change spark plugs or something like that? something that could have been taken loose and not reinstalled correctly?
    Scott-Mississippi
    1996 Silverado
    *Mostly stock for now
    *Soon to be airbag project..

  7. #7
    Legend cascott325's Avatar
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    Lawrenceburg, Kentucky
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    Default

    i think mine does the same thing. at around 40 mph in 4th gear is when it does it. it kinda comes in bursts, but only when i am going up a slight grade. i dunno how to explain it really
    2000 silverado with a 5.3l v8, shorty headers, upgraded plugs, 10 mil wires, magnaflow high flow cats, flowmaster 80 series muffler(2 in 2 out) w/ 18 inch stainless silverline tips. i have a k&n CIA. its a 4x4 z71 offroad package. Ls model.
    extended cab 160k miles, truxedo low profile bed cover, diablo sport predator tuner.
    reman tranny @ 130k miles
    Chris

  8. #8
    Sr. Mechanic sc99z71's Avatar
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    Default

    It started when I changed the spark plugs and I tried to go cheap with the plugs and bought Autolites. Now I have replaced those with AC Delcos and it went away for about 2 weeks but now its back. Maybe a plug wire change might work. Also it doesn't do it at any other speed even if its at the same rpm that it does it at 45-55. I tried that yesterday.

  9. #9

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    Quote Originally Posted by sc99z71 View Post
    It started when I changed the spark plugs and I tried to go cheap with the plugs and bought Autolites. Now I have replaced those with AC Delcos and it went away for about 2 weeks but now its back. Maybe a plug wire change might work. Also it doesn't do it at any other speed even if its at the same rpm that it does it at 45-55. I tried that yesterday.
    you need new plug wires!!! if you are not careful when removing and rehooking the plug wires you can break off the tips inside and they wont make the proper connection. I JUST FIXED THIS SAME PROBLEM FOR A FRIEND LAST WEEK!

  10. #10
    Sr. Mechanic sc99z71's Avatar
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    I will be picking them up soon!! And not the cheap ones!! Luckily with the weather being warm my truck gets to sit in the driveway while I ride the motorcycle. Thanks for the help, I will report when I put on the new wires and if the problem goes away.

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