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Need help from the Carb Pros out there

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by MilpitasK5, Jul 26, 2002.

  1. MilpitasK5

    MilpitasK5 1/2 ton status

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    I have a similar post about getting my carb rebuilt but I just got back from the smog shop and they're telling me that my idle speed is too high. I've had it adjusted but it sticks up around 1200. When I tap on the peddle, it drops back to 1000 rpm.
    I have an Quadrajet on an 86' K5 with a 5.7L. Here are more details:
    When I start up the truck in the morning, it putts (idle up and down with black smoke puffing out. sometimes donuts will come out!) until it warms up a little, then the idle jumps to 1500 until it warms up more, as soon as it's all warmed up, it drops to 700-1000. When the idle is up, it back fires a few times. When it's warm and I stomp on the peddle, it will gurgle before it opens so a takes a few seconds to go. If I stomp on the peddle and let off quickly, it'll back fire or if not, just gurgle... I think there is a vaccume leak too. When I spray carb cleaner on the driver side of the carb, the idle gets thrown off and kinda wants to die out. We've changed the carb gasket and it lessened the vaccume leak but it's still there. /forums/images/icons/frown.gif
    Grim was telling me I might have a choke prob too. What do I do to peep that?
    Any help or suggestions will be greatly appreciated!! /forums/images/icons/smile.gif
     
  2. Blue85

    Blue85 Troll Premium Member

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    I don't know what's wrong, but it should be helpful to watch the operation of the choke and the throttle linkage while warming the engine up from cold. Also, you can use a rubber tube or a stethoscope (tube opening) to probe around for the vacuum leak. Otherwise, they are very hard to find because of the hissing in the carb.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Sounds to me like the choke coil is a little too tight.

    If the choke is a problem, the choke blade will not be vertical when the idle is higher than normal.

    If you have some idle change when spraying around the drivers side, it may be the primary throttle shaft...if its horribly worn (mine was on a Q-jet I had) the idle will not be very consistent, and you could see some vacuum leak there. Even when mine was horribly worn, I didn't have any problems in the vacuum arena, it was just the idle that wouldn't stay constant.
     
  4. MilpitasK5

    MilpitasK5 1/2 ton status

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    Will do, Blue! Thanks for the input.
    So Dorian, is that primary throttle shaft way the **** in there or is it easily accessed.
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Need help from the Carb Pros out there *DELETED*

    Post deleted by dyeager535
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Carbs gotta come off and entirely apart. Not hard, but you've got to do that to get in there and re-bush it, or pay someone else to do the bushing.
     
  7. MilpitasK5

    MilpitasK5 1/2 ton status

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    Okay. Where can I get a book on my carb?? This sounds interesting. maybe I can do this myself??
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    I don't know that any book will cover re-bushing. AFAIK, it was never a factory procedure. Not sure why the Doug Roe book doesn't cover it (put out by HP Books) but I didn't see any info in there on it.

    Carbs unlimited (http://www.carbsunlimited.com/) sold me two bushings for $5 a couple years back. Not sure if they can get the drill bit, but I bought the bushings, measured the OD of it, and matched that up to a drill bit, and drilled the hole out to that diameter. *Think* it was a "J" drill bit, which isn't real common.
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    I *think* its "Rochester Carburetors" and I know Doug Roe is the Author and HP Books is the publisher. You can search for it on Amazon, but I paid something like $15 for it at the local speed shop.

    Great reading if you like learning how and why things work, and ways to change/improve them for your personal use.
    Apparently the Haynes Rochester manual is great too, but I've never read it, so no comment.
     
  10. MilpitasK5

    MilpitasK5 1/2 ton status

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    Thanks for the advice. I'll start digging! /forums/images/icons/smirk.gif
     
  11. Khi5in

    Khi5in Registered Member

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    just one thing to think about before going crazy with the carb.You may have some carb problems too but do yourself a favor and do a compression test on each cylinder. You may have a valve hanging up somewhere. I only say this because you said it blows smoke rings sometimes witch tells me the exhuast is sucking in as well as blowing out whitch will cause the smoke rings and sucking exhaust usually comes from a valve not seating correctly.
     
  12. MilpitasK5

    MilpitasK5 1/2 ton status

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    Thanks! I'll do that before anything. /forums/images/icons/blush.gif /forums/images/icons/shocked.gif
     

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