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Old 10-25-2006, 03:20 PM
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Q-jet problem

I've got a 1981 Cadillac hearse with the electronic Q-jet. I bought the car last April and had a mechanic friend that I've known for about 12 years do a rebuild on it. It worked fine all summer, but now that it's getting cold, it's acting up. When the engine is cold it runs very rich, black smoke out of the exhaust for about 5 minutes or so. Then it clears up, and catches fast idle and works properly. It's gassing me out of my garage when I start her up to leave for work every morning. My mechanic buddy said he'd check it out, but if I take it to him the motor will be warm, and it only screws up when it's cold. And it's almost impossible to catch him away from work. I've got $120 in the rebuild already, and would like to get it working right, vs getting a non-electronic carb and trying that. Hopefully one of you Q-jet experts will be able to point me in the right direction. Thanx...

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Old 10-25-2006, 03:58 PM
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sounds like the choke is set too tight. When its cold, open the throttle, the choke butterfly should close. If it snaps closed real hard, its too tight. Loosen it up so it closes, but not too hard.

A lot of chokes give people trouble in the spring and fall.............weather is between where they are usually set for.
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Old 10-25-2006, 04:32 PM
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With what was mentioned above, also check the operation of the choke pulloff. It's a small round pancake looking thing on the pass side that has a vac. hose going to it. Once running, it should pull the choke open some so it doesn't drown the engine with gas. Easy to replace and cheap too.

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Old 10-25-2006, 05:56 PM
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Also check to make sure the electric connection is kosher. The electric part of the Qjet controls idle mixture.
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Old 10-25-2006, 07:24 PM
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Doc here,

Be sure you have power to the choke heater (only while running) Element . If not, check the choke relay and/or fuse..

If it is working , it should pull open within 3 to 4 minutes (light stroke on the throttle, to slip the detents) If it is not working, It will take much longer (from just transmitted engine heat) but will pull in like 10 minutes or so..

Pull the air cleaner top and watch from a cold start.

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Old 10-26-2006, 01:11 PM
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OK here we go.. 1- choke wire has power with ignition on. When I installed carb after rebuild found that original lead sometimes had power, and sometimes not. Found another hot lead thru ignition and tapped into it....2-My carb has 2 pulloffs, Haven't checked recently, but they both were working a couple months ago...3-Might be set too tight. Last time I had problems with it, I took it to my mechanics house and discovered dead lead going to choke, and we found another hot lead and he set choke then. Engine was warm, and it was in summertime. He's coming over this Saturday for a Halloween party I'm having. Maybe I can get him to come back on Sunday morning when the engine's cold, and we can go thru it. Thanx for the help guys....
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Old 10-26-2006, 02:03 PM
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Most likely the vacuum pull off is not working. This was a very common issue. it may also be missadjusted. This can be checked even if the car is warm. Just have someone start the car while watching the pull off arm. It should suck in as soon as the vehicle starts and it should be sufficient to open the choke 3/16s of an inch or so.
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