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rough running TBI 350

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by G-Force8, Dec 17, 2006.

  1. G-Force8

    G-Force8 1/2 ton status

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    Whuz up gang

    Trying to trouble shoot the shimmy in my 3-fitty

    My '91 Burbs' TBI 350 started running rough ( physically shaking ) at idle. It runs smooth under acceleration,but with noticable power loss ( of course it is stock and about to hit 200K mi ) and a slight hissing that I suspect may be the throttle body gasket. I put new plugs and wires in, and it improved some,but not enough. I just bought a new O2 censor thinking that might help,but haven't installed it yet. I'm thinking I could pull the plugs and check the gapping.

    what do you guys think

    any suggestions?
     
  2. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    It sure sounds like a vacuum leak to me. Have you taken the time to check all you vacuum lines and fittings?
     
  3. G-Force8

    G-Force8 1/2 ton status

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    nope, have not looked at a single vaccuum line

    I will do that when I plug in the new O2 censor in a few days

    thanks for your .02$
     
  4. CB77GMC

    CB77GMC 1/2 ton status GMOTM Winner

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    2X :D
     
  5. NEK5

    NEK5 3/4 ton status Premium Member

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    third that:D
     
  6. Thunder

    Thunder 3/4 ton status

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    Ummm..... maby replace the TB gasket? That will cause a rough running /high idle. As said check/ replace your vaccum lines. Also might want to pull the IAC and clean it. They get carboned up and leak.... But...... The first thing you should do before anything, is check for trouble codes.
    A new fuel filter would not hurt either.
     
  7. G-Force8

    G-Force8 1/2 ton status

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    Thanks for the replies guys.

    I went ahead and bought a new TB gasket for good measure. Though, it hasn't had any problem high-idling,just shaking at idle. I replaced the fuel filter last year when I put in a new fuel pump.

    Without fail, a new O2 censor, new TB gasket and probably new vaccuum lines will be replaced with an oil change this weekend.

    We'll see
     
  8. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    How did you get on? I had a bad idle at start up for years. It would run on 7 for anything from 5 to 30 seconds then clear itself. If you drove off before it was up on 8 it would not clear at all. I used to replace the plugs and it would be better for a week or so then back to acting up.
    I tore that motor down last week as I've just blown my newly rebuilt motor:doah: and needed some parts, and found that I had a massive crack in the head allowing coolant to get into the cylinder when not running.
    Funny thing is I never had oil in the coolant and never had coolant frothing up my oil. Weird.
     

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