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91 K5 pinging problem...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by DB1, Feb 13, 2001.

  1. DB1

    DB1 Newbie

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    I've got a stock (not for long) 91 K5 with 30k miles that sounds like a damn diesel under light load. I backed off the timing 3-4 degrees and it seems to have helped a little. I ran 93 with a booster and that seems to have helped a little too. I also changed the plugs (no diff). The ECM says all is good to go. Any ideas? Does anyone have a source for tech info on 91 engines/TBI/ECM?
     
  2. Mr Red

    Mr Red 1/2 ton status

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    Hate to hear that. I recently bought a 91 so I'm look'n @ diff. world than my '86. That said, I noticed the owner's manual says 87 or higher Octane. Usually it more specific. I'd suspect carbon buildup. But, with only 30K miles, has this been sitting??? If I was a bett'n man, I'd say, there's your problem. Lifters probably locked up or something. What I'd try is BG44K fuel system cleaner with a couple tank fulls of gas. If no luck there, I'd try the GM Top Engine Cleaner; available at your dealer (there's a can in my garage with my '91's name on it just for general purposes/cleanliness). Just ideas. You probably need better guidance but if its been sitting, I'd be weary of stuck lifters; what to do, I'm not sure.

    Good Luck,
    [​IMG]
    <font color=red>David, '86 & '91 K5</font color=red>
     
  3. Stoopalini

    Stoopalini 1/2 ton status

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    First make sure you're using high octane gas and not the cheapest stuff out there. That alone will sometimes make a difference.

    If it's not the gas, then the next thing I would do is adjust the valves. My '88 Jimmy w/350 TBI was clanking like crazy. After a valve adjustment, all nice and quiet.

    It's pretty easy to do if your inclined .........

    Thomas.

    -- '84 K5 Blazer --
    <A target="_blank" HREF=http://Stoopalini.coloradok5.com>http://Stoopalini.coloradok5.com</A>
     
  4. DB1

    DB1 Newbie

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    Thanks for the info. It did sit for awhile. I bought it in April 00 with 19K. I'll try the cleaner and see what happens.
     
  5. HarryH3

    HarryH3 1 ton status Author

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    Make sure that the EGR valve isn't stuck. Without EGR at part throttle the engine will ping a lot. You shouldn't need more then 87 octane if it's the stock engine.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  6. Sparky

    Sparky 1/2 ton status

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    Is there a knock sensor on a 91? I dont know much about them, but that might be the problem.

    When all else fails... Check the blinker fluid.
    78 K-5
     

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