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HELP she buckin', she buckin'

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by foxman, May 8, 2002.

  1. foxman

    foxman 1/2 ton status

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    HELP she buckin\', she buckin\'

    My 90 K5 is buckin'n! This problem seems to be occuring in the trans and when I am cruising with my foot on the gas, but only slightly on the gas. It's like speeding up to 35 then feathering the throttle to maintain speed. this is when the enging surges and bucks like a damn bull on crack. The engine seems to cut out and come back rappidly, almost like an out of time engine, yet timing is set perfectly. This problem excelerated after I eliminated the Cat, (Maybe have something to do with it?) I'm guessing a vaccuum problem due to worn cam lobes/leaky valves. The trans is electronically controled, not vaccuum, so no modulator... Any master K5 mechanics have a tip for the ol' foxman??
    thanks.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: HELP she buckin\', she buckin\'

    If you can get your hands on a real-time scanner, do that. Could be a few different things, and since your truck allows you to "see" whats going on, its a good starting point.
     
  3. 87GMC

    87GMC 1/2 ton status

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    Re: HELP she buckin\', she buckin\'

    I've got a similar problem. Like a bad miss. At low RPMs barely noticeable but as RPMs increase it gets progressively worse. The harder I am on the gas the worse it is, but at mid-high RPMs it gone and runs fine. Like the timing is off, but then comes back in. I don't have a tach but I'm guessing about 3000-3500 it when it stops. I've got a manual though, so if it's the same problem, it's not the tranny. Hopefully someone can help us.
     
  4. SkulzNBonz

    SkulzNBonz 1/2 ton status

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    Re: HELP she buckin\', she buckin\'

    Sounds alot like a fuel delivery problem. Clogged fuel filter or fuel pump gettin' ready to die.

    John
     
  5. 87GMC

    87GMC 1/2 ton status

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    Re: HELP she buckin\', she buckin\'

    Won't a fuel pump problem get worse as RPMs and fuel demand increased?
     
  6. SkulzNBonz

    SkulzNBonz 1/2 ton status

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    Re: HELP she buckin\', she buckin\'

    RPM's and fuel demand can be greater at lower speeds because you are using more fuel and turning higher rpms to get to speed, creating more demand on the fuel pump. As you reach a cruising speed, final gear ratios lower your RPM's and fuel consumption to maintain speed. That is the way I understand it. If that isn't correct, at least it sounds good /forums/images/icons/laugh.gif!!!

    John
     
  7. jc71355

    jc71355 1/2 ton status

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    Re: HELP she buckin\', she buckin\'

    My 91 is doing something similar. At about 50 i'll go to accelerate lightly and it acts like it is missing then i'll go ahead and give it more gas and it downshifts and runs fine. I've only had it do it to me after about an hour or so of driving. Just going around town it hasn't done it to me. I'm stumped.

    James
     
  8. k5ntexas

    k5ntexas 1/2 ton status

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    Re: HELP she buckin\', she buckin\'

    i have a carbed engine and this same thing was happenin to me. it was the fuel pump. it was crappin on me. and also i had a crimp in my fuel line so that had a lil bit to do with it as well. check the fuel pump first. hope this helps. later.

    jacob
     
  9. driney

    driney 1/2 ton status Premium Member

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    Re: HELP she buckin\', she buckin\'

    I had an 89 GMC with the same problem. Replacing the throttle position sensor fixed it.
     
  10. Thunder

    Thunder 3/4 ton status

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    Re: HELP she buckin\', she buckin\'

    The pick up coil in the distributor will also cause these type of problems. It will usually throw a code 42 but may not turn on the check engine light. Usually gets worse as the vehicle warms up
     
  11. KMH87K5

    KMH87K5 Registered Member

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    Re: HELP she buckin\', she buckin\'

    I had the same problem with my 87K5. I found that the dist cap and rotor were all corroded, so i went ahead and gave her new cap, rotor, plugs, and wires. Truck runs great now. I would check these things out first. Also, the truck would stall at low idle, it sucked when i was in traffic, so i disconnected the egr valve and it solved that problem. Fuel filter might also need to be changed
     
  12. MudbogAD

    MudbogAD 1/2 ton status

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    Re: HELP she buckin\', she buckin\'

    I was thinking of a fuel filter or even a fuel pump.
     
  13. ArrowheadK5

    ArrowheadK5 1/2 ton status

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    Re: HELP she buckin\', she buckin\'

    What you described happened to me, too.
    Butthe problem was, the tilt wheel got really loose really fast and suddenly the ignition started switching on and off when I went over bumps or turned left. Since it has a manual tranny, this made for a very rough ride. It would "buck" like you said and then connect again and keep running. A new column fixed it.
    probably not your case, but I thought I'd throw it out there.
     

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