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Choke Problems NEED HELP!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BRN78BLAZER, May 6, 2003.

  1. BRN78BLAZER

    BRN78BLAZER 1/2 ton status

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    From what I can tell, when I start It in the morning the choke does fully close. Then the vacumm breal opens it right away about 3/4 wide open. It will idle around 1500 for 5 sec. then slowly start stumbling and idling down. When it's about to stall(which it will) I can give it a bit of gas and it will go back up to 1500 and then will do the same thing again 4 or 5 times until it idles around 10-1200 kinda rough, but won't stall anymore. Its a new carb 2bbl and I used the specs from a rebuild kit to set everything.

    Also when you first drive it it's kinda hesitant, after about 1 mile it will be on low idle, kinda lumpy at 650-700. Then after say another mile it idles nice and smooth at 750-800 rpm.

    Any input is appreciated, I wish I could figure this out.
    Thanks, Steve
     
  2. jakeslim

    jakeslim 1/2 ton status

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    i got tired of choke problems after trying to clean, tune and whatever with the carb (quad). I bought a new edelbrock quad and it starts instantly and idles great. Really made all the difference in the world.
     
  3. BRN78BLAZER

    BRN78BLAZER 1/2 ton status

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    I'm thinking about switching to a 4bbl, but with the 2bbl there is no smog equipment at all, whereas witha 4 there is, and I don't want to put any of that stuff on. But they are now doing roadside checks on older vehicles which means I couldn't even put a 4bbl without the smog stuff.

    Someone out there must have an idea. Being such a new carb Its gotta be sumthin simple I'm overlooking.
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    Sounds to me like the vacuum break is set to open it way too far.

    At least on the quadrajets, the opening of the choke is much smaller initially. Maybe 1/8" or less.
     
  5. BRN78BLAZER

    BRN78BLAZER 1/2 ton status

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    I followed the instructions to set it. Close choke, on fast idle, then seat the vacumm break using an outside source. Then adjust the linkage and check how far open the choke is with a drill(i forget what size).

    After doing all this it will still open up about 3/4 of the way once you start it. Could it be that the actual vacumm break needs replacing??

    Thanks, Steve
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    If the vacuum pulloff is malfunctioning, it won't hold vacuum, so you can test it pretty easily.

    When you set it, did you adjust that linkage as it would be when the pulloff was retracted? It would have to be pretty far out of whack for the linkage to pull it that far open if its not supposed to.
     
  7. BRN78BLAZER

    BRN78BLAZER 1/2 ton status

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    The vacumm break pulloff is working. I'm thinking I must have not set it correctly, the specs say it should open the choke 11/64", not like 3/4" which I'm getting. I'm sure I followed the instructions correctly but I'll try it once more.

    One more thing I'm not sure on is setting the idle mixture. For the best idle whats better lean or rich? It's my understanding that these screws only control the idle mixture, and don't effect the performance at any other time like coasting or acelerating? Am I on the right track here?
    thanks, Steve
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    Again, based on Q-jet's, I lean them out as far as I can..until it starts to stumble and miss, then I richen it up just a hair.

    Believe the factory method is set them for max vacuum.
     

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