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Quadrajet idle mixture

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Old 06-13-2012, 08:21 AM   #1
Capt Ken
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Default Quadrajet idle mixture

Car smells like it is running rich at idle. I see where to adjust the idle mixture, but no screw driver slot. All I see what looks like a thin oval head on the metering screw. Do I need a special wrench? My neighbor has a 69, he mentioned the epa covers that were on his. I don't think that is what I am seeing.
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Old 06-13-2012, 08:36 AM   #2
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Does it look like a "D"? That is a specific tool to keep regular people from messing with the mixture.

Has the carb been rebuilt? If not then it may not be as simple as adjusting the mixture...even if it has been rebuilt, if may not be that simple.
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Old 06-13-2012, 08:37 AM   #3
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it does take a special adapter to fit on the adjustment screws. i bought a flexible shaft adjustment tool with several different tips @ orielly auto. one of the tips fits the quadrajet mixture screws. also helps to have a vacuum gauge to get the best setting.
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Old 06-13-2012, 09:29 AM   #4
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What year car is it (if it's an 81 and the carb is a E4ME that's a whole different animal), is it the original carb, what's been changed lately, did it just start "smelling" rich, are there other indications or performance issues? Help us help you.

The short answer is you might need a special screw driver, but that depends on what you have. You might have to remove caps to get at the mixture screws. Also, you should know that smelling rich doesn't necessarily mean it's rich. A lean condition can cause that too.
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Old 06-13-2012, 10:47 AM   #5
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Quote:
Originally Posted by Capt Ken View Post
Car smells like it is running rich at idle. I see where to adjust the idle mixture, but no screw driver slot. All I see what looks like a thin oval head on the metering screw. Do I need a special wrench? My neighbor has a 69, he mentioned the epa covers that were on his. I don't think that is what I am seeing.
Remove the screws, using some long, thin needle nose pliers, or some vacuum tubing that will fit snuggly over the screw head, or a piece of hard fuel line squashed down to fit the screw, whatever, use your imagination and get the screws out somehow, and you can very carefully grind a screwdriver slot into the head of the screw with a thin hacksaw blade, or a wizwheel, if you put the screw in a vise and are very careful. Then re-install the screws, lightly seat them, back them out, eh, 3 turns? Begin tuning from there. If possible, screw them all the way in before you remove them, and count how many turns it takes to lightly seat them. Then re-install them the same number of turns out, and get to tunin'!

Doesn't it **** you off, dealing with something that somebody else intentionally made more difficult, just to try to keep you from screwing around with it? Now you'll be able to adjust your idle screws with a flat tip screwdriver, as God intended!

P.S. Spray a little carb cleaner through the hole that the screw comes out of, and clean the screw up, too, it's probably pretty cruddy!


Keep the shiny side up!
Scott
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Old 06-13-2012, 10:59 AM   #6
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Can't answer most of the history questions. Car runs fine on the road, just smells rich idling when I'm working on it, just wanted to check the mixture.

Carb # is 17084288 1994 HKF
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Old 06-13-2012, 12:32 PM   #7
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I see where to adjust the idle mixture, but no screw driver slot. All I see what looks like a thin oval head on the metering screw. Do I need a special wrench?
Yes. Go to NAPA and buy a carb idle screw adjusting tool. It's about $10.

But...
I'll bet your problem is not with idle mixture - it's almost impossible to adjust a lean-run '84 carb to run so rich at idle that you can smell it. More likely, your timing is off or you have internal carb problems.

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Old 06-13-2012, 03:25 PM   #8
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Thanks Lars for the wrench tip. The carb is on a '73, why do you think it is a "lean run 84"?

SpeedReed, I didn't have a vacuum gauge growing up. It was always turn the screw in til the engine got rough, then back out a 1/4 turn. What am I looking for when I'm setting the mixture....I would guess, max vacuum?
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Old 06-13-2012, 05:07 PM   #9
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Thanks Lars for the wrench tip. The carb is on a '73, why do you think it is a "lean run 84"
Because you posted your carb number above: 17084288. That's a 1984 truck carb and it's set up to run lean enough to meet '84 lean-burn emission standards.
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Old 06-13-2012, 06:12 PM   #10
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yes max vacuum for each screw setting, BUT listen to Lars, he's the quadrajet expert. what he says goes.
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Old 06-13-2012, 08:45 PM   #11
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I've set mixture with a dwell tach with good results. listen to Lars.
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Old 06-14-2012, 08:34 AM   #12
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Thanks,
So it sounds like the best course of action is to buy the tool and check the adjustment. If it still smells rich, plan on a rebuild.
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Old 06-14-2012, 08:41 AM   #13
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Thanks,
So it sounds like the best course of action is to buy the tool and check the adjustment. If it still smells rich, plan on a rebuild.
As suggested by Lars, I'd be checking the timing too. If you do end up rebuilding it, what are you going to buy the kit for? Your car or an 84 truck? You'd do well to email Lars for his recommendations and papers on tunning and rebuilding...just say'n....
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Old 06-14-2012, 04:57 PM   #14
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Now that I know it's an 84, that's the kit I would order. The car has a crate motor in it, just over 1200 miles since installed. Checking the dwell, timing, etc was one of my first chores. It is now on spec, still smells.
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Old 06-14-2012, 05:27 PM   #15
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Ken, I'd still suggest pinging Lars for his Q-jet papers. He forgotten more about these things than most of us will know, and he's willing to share. It'll save you time and headaches I promise.
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