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Q-Jet Choke?

Discussion in 'The Garage' started by Russell, Feb 13, 2006.

  1. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Hey guys, anyone wanna help me figure out my choke on my 77?

    I'm spoiled with EFI, and haven't the slighest clue what I am doing, LOL

    The truck started pretty good on cold mornings, but was choking the engine too much. Made it run rough, and black smoke come outta each pipe for about 2 - 3 minutes till the engine warmed up enough to start opening the choke up.

    I figured I'd "fix" it, but now the thing doesn't choke at all, or high idle. Choke plate is open all the way. No idea how to adjust it, or how the linkages work :doah:

    I need the choke set for tommorow morning, suppost to get DANG cold outside tommorow, and I won't be able to get the truck started very easily without it, lol! Been fairly warm recently, so it hasn't been a problem.

    The Q-Jet has a hot air choke mechanism BTW :)
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    After it cools off, kicking the throttle should snap the choke shut. That spring pressure to shut them is handled by the coil. If it won't snap shut when cold with the throttle, need to tighten up the choke coil until it JUST snaps shut. If it comes close, you are probably better off fine tuning the linkage between the coil and the choke plate.

    THEN you start dealing with the fine tuning of the pulloff, and choke idle speed.
     
  3. Blue85

    Blue85 Troll Premium Member

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    You should start by spraying down the linkages on both sides of the carb with some cleaner to make sure nothing is sticking.

    What did you do to "fix it"?
     
  4. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    I just loosened the coil a bit in an attempt to keep it from closing the blades so much.

    I set it by giving it part throttle so it goes striaght to high idle, then carefully turning the coil till the choke plate goes where I wanted it to be, about 1/8th of an inch open.

    I'll go fiddle with it this morning when I first fire it up. Its about -20C outside, so it'll take a few minutes for the engine to warm up enough to start shutting the choke off.
     
  5. goldwing2000

    goldwing2000 Guest

    With the engine completely cold, push the throttle to the floor. That should close the choke completely.

    If the choke plate is not closed completely, turn the coil until it is just closed.

    If the plate is completely closed, back the coil off until the plate just opens and then turn it back until it is just closed.

    Readjust the same way when the weather warms up.
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    In a perfect world, no adjustment should be necesarry depending on weather.

    Choke coil works on heat whether electricity is applied to it or not, regardless of temp. As old as this stuff is now, unmolested or tuned correctly Q-jet apps I've seen don't have hot/cold choke issues, (if the stuff is still in good shape of course) nor would it have been tolerated by new car buyers.

    Solely tightening or loosening the choke coil affects the "throw" of the choke plate, which means choke full open or full closed can be off even if the other is dead on.

    Once the vehicle can be brought up to operating temperature is when you figure out if the linkage is right or not though, as you'll be able to see if it opens fully.
     
  7. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Thank you fellas!

    I got the choke working again this morning -- Somewhat, lol

    Its still got a mild puff of black smoke, not as bad as before though. Now that I know how to make it work period, I can fiddle with it tommorow morning to get the choke plate set properly :)
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    I found that once the choke is adjusted properly, the fast idle can be turned down quite a bit. I think mine fast idled at about 1200RPM when I was done, but it was plenty.

    Some I've seen up around 2000RPM, but except for emissions and faster warmup, I think it's a bit unnecessary to rev it that high continuously right at startup.
     
  9. goldwing2000

    goldwing2000 Guest

    In a perfect world, yes. But in a normal world, people will generally tolerate a lot of bs when it comes to vehicle tuning. It doesn't hurt anything to re-check your choke and make sure it's set the right way for the right time of year. And since he has a hot air choke and not an electric, it's more finicky about ambient temperature.

    Heck, even Edelbrock recommends re-checking the choke operation when the seasons change.

    There's no such thing as having it set "too correctly". :D

    Anyway... that's how I've always set mine (and it will definitely get you in the ball park) but looking around the web, there seems to be a few different methods. If you have some time, check autozone's web site and they should have your procedure listed. Try this link. Try other years, too.

    Here's a picture:
    [​IMG]

    Good luck!
     

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