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Quadrajet help

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Old Jan 8, 2014 | 09:58 AM
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Car: 1986 Trans Am
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Quadrajet help

Hello all,
I'm afraid this is going to sound like a totally dumb question but I've tried and tried and cannot figure it out. I need to remove my air cleaner to mess with the choke, which I believe is not opening (hard starts, runs very rough and misses while spewing black and blue smoke, but runs perfectly fine once warm) and for the life of me, I cannot figure out how to remove the air cleaner. There is only one piece that is stumping me because I don't know how to detach it from the air cleaner. I am pointing to it in the attached picture.
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Old Jan 8, 2014 | 02:03 PM
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Re: Quadrajet help

It just pulls apart. Filter will stay intact inside the air cleaner.
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Old Jan 8, 2014 | 02:47 PM
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From: Central Arkansas
Car: 1986 Trans Am
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Re: Quadrajet help

Thanks! I have now successfully removed it. Now to figure out why my choke won't open...
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Old Jan 8, 2014 | 02:49 PM
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Re: Quadrajet help

is it electric choke
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Old Jan 8, 2014 | 03:06 PM
  #5  
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From: Bellingham Ma
Car: 1986 IROC-Z
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Re: Quadrajet help

the filter needs to be replaced BTW
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Old Jan 8, 2014 | 03:18 PM
  #6  
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From: Central Arkansas
Car: 1986 Trans Am
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Re: Quadrajet help

It's a computer controlled quadrajet, so yes i believe it has an electric choke.

The filter looked fine to me when I removed it, did I miss something?
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Old Jan 8, 2014 | 03:22 PM
  #7  
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From: Bellingham Ma
Car: 1986 IROC-Z
Engine: 5.0 4bbl
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Axle/Gears: 2.73 G80
Re: Quadrajet help

Originally Posted by AssaulT/A
It's a computer controlled quadrajet, so yes i believe it has an electric choke.

The filter looked fine to me when I removed it, did I miss something?
the breather fitler
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Old Jan 8, 2014 | 03:35 PM
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From: Central Arkansas
Car: 1986 Trans Am
Engine: 305
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Axle/Gears: 3.08? unlimited slip
Re: Quadrajet help

Are you just referring to the air filter? Because it's not clogged.
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Old Jan 8, 2014 | 04:15 PM
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Car: 1986 Trans Am
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Axle/Gears: 3.08? unlimited slip
Re: Quadrajet help

Okay so I got the car started and then got out to mess with it. I moved a little lever on the side of the carb (choke lever) with the letters AD on it to the opposite of what it was, and then cranked it. It was idling fairly smoothly at about 400 rpm (too low, I know) but when I gave it some gas it died. any advice? Is the choke lever just stuck?
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Old Jan 8, 2014 | 04:19 PM
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From: Bellingham Ma
Car: 1986 IROC-Z
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Transmission: 700-r4
Axle/Gears: 2.73 G80
Re: Quadrajet help

Originally Posted by AssaulT/A
Are you just referring to the air filter? Because it's not clogged.
no the tiny filter where you were pointing at
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Old Jan 8, 2014 | 07:42 PM
  #11  
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From: Central Arkansas
Car: 1986 Trans Am
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Axle/Gears: 3.08? unlimited slip
Re: Quadrajet help

Ahh I understand now. Sorry. Yeah it does look pretty dirty, I'll see about cleaning/replacing it.
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Old Jan 8, 2014 | 07:52 PM
  #12  
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From: Central Arkansas
Car: 1986 Trans Am
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Axle/Gears: 3.08? unlimited slip
Re: Quadrajet help

Let me preface this post by saying that I've looked all over this forum and the rest of Google, but I'm still confused. I believe that I need to adjust my choke to fix my problem, but I'm having problems finding the choke. I think I found the choke lever, I've attached a picture where I'm pointing to it. It's a small lever with about 90 degrees of movement and the letters AD stamped on it. I've also attached a picture of that side of the carb for reference. I apologize for all the questions, I'm trying to learn as much as I can as I go.

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Old Jan 8, 2014 | 09:09 PM
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Re: Quadrajet help

Yes, you are pointing at part of the choke linkage. The choke housing is the circular piece that has the black cover with three rivets holding it in place. It also has the spade terminal sticking out with the one wire attached. It would appear that your carburetor has never been rebuilt since the thermostatic coil (black piece) is still riveted in place. A rebuild requires the complete disassembly and thus the coil would have been held in with screws. Before you do anything you need to verify if the choke is operating properly. With the engine cold and the air cleaner assembly off as in the pic, press the accelerator pedal all the way to the floor and release it. You have now set the choke for proper operation. Crank the engine without touching the gas pedal. The car should start and idle at the fast idle spec on your emission decal. Do this procedure exactly and report what happens.
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Old Jan 8, 2014 | 09:24 PM
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From: Central Arkansas
Car: 1986 Trans Am
Engine: 305
Transmission: T5
Axle/Gears: 3.08? unlimited slip
Re: Quadrajet help

Thanks for your help! I did what you said (which is my usual starting procedure in the cold) and it fired, idled for half a second (at most) and died. It has behaved similarly all this winter, but usually I give it gas and it will miss badly but run (extremely roughly, shaking the whole car violently and belching bluish smoke), but after 1-3 minutes it would warm up and idle smoothly at ~800 rpm.
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Old Jan 8, 2014 | 09:38 PM
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Re: Quadrajet help

When you set the choke for cold start up, the piece you were pointing to should be at the top (looks like it was in your photo) and the choke blade itself should be completely closed. If you take your finger and push the linkage down, you should feel two "steps". These are the steps on the fast idle cam. As you push that linkage down, the choke blade should open until it is all the way open with the linkage pushed all the way down. Does this happen?
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Old Jan 8, 2014 | 09:49 PM
  #16  
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From: Central Arkansas
Car: 1986 Trans Am
Engine: 305
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Axle/Gears: 3.08? unlimited slip
Re: Quadrajet help

I'm not sure I know which is the choke blade
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Old Jan 8, 2014 | 09:54 PM
  #17  
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Re: Quadrajet help

It is the metal piece that covers the opening on the primary side (closest to the front of the car) of the carburetor. I can see it in the third pic you posted. It looks brown or rusty.
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Old Jan 8, 2014 | 10:05 PM
  #18  
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Car: 1986 Trans Am
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Axle/Gears: 3.08? unlimited slip
Re: Quadrajet help

I think I understand. I thought that was the primary rather than the choke lol. I am very appreciative of your help, and will check on the choke tomorrow morning. (It's 28 degrees and sleeting where I live, and my parent's house doesn't have a garage)
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Old Jan 8, 2014 | 10:12 PM
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Re: Quadrajet help

Yes, the choke blade covers the primary side when closed. Let us know what happens. I am out of town right now but I can post some pics of these items on my own carb once I am home in a few days if you are still having problems finding them by then.
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Old Jan 8, 2014 | 10:24 PM
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Re: Quadrajet help

Do this before you start to turn screws and bend rods and drill rivets in an attempt to fix whatever is ailing you, take a few minutes to do this:

Remove the hose from the choke pull-off (see your photo) and apply vacuum to it. Confirm that the choke pull-off isn't punctured. My guess is that this is the root cause of your cold start problem.

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Old Jan 9, 2014 | 09:23 AM
  #21  
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Car: 1986 Trans Am
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Axle/Gears: 3.08? unlimited slip
Re: Quadrajet help

Okay I pressed the throttle all the way to the floor to set the choke, went around to check, and the choke blade was totally closed. That would explain why it doesn't want to start. I rotated it by hand and it my be either my imagination or totally normal, but the action of the blade felt a little sticky.

Paulo, how would apply vacuum to the choke pull off like you suggest?
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Old Jan 9, 2014 | 11:23 AM
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Re: Quadrajet help

The choke should be totally closed on a cold engine. The function of the choke pull off is to slightly open the choke once the engine fires (and vacuum is applied).

Test the pull off by 1) removing the vacuum line 2) pressing the rod into the the pull off 3) placing your finger over the nipple the vacuum line was hooked to 4) releasing the rod. The rod should stay in it's retracted position until you remove your finger from the nipple. If the choke pull off is bad, replace it.
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Old Jan 9, 2014 | 03:23 PM
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Re: Quadrajet help

Originally Posted by AssaulT/A
Okay I pressed the throttle all the way to the floor to set the choke, went around to check, and the choke blade was totally closed. That would explain why it doesn't want to start. I rotated it by hand and it my be either my imagination or totally normal, but the action of the blade felt a little sticky.

Paulo, how would apply vacuum to the choke pull off like you suggest?
The choke is supposed to be completely closed before you start the engine, provided the engine is cold. Once then engine starts, vacuum is applied to the pull-off diaphragm which opens the choke slightly. After this, the choke operation is taken over by the choke thermostat (that round black thing in front of the pull-off diaphragm with one wire connected to it). As the engine warms up, the choke will gradually open by itself.

The action of the choke blade feeling sticky is normal (when the engine is cold). That's the high idle adjustment screw dragging on the high idle cam.

If you don't have a vacuum pump like a Mityvac, leave the hose connected to the carb. Have a helper start the engine and observe the arm of the pull-off. The arm should move into the pull-off diaphragm immediatly after the engine starts.

If the pull-off isn't opening the choke slightly, no air is getting through the carb and the engine is over-choked (too rich). That's the cause of your running rough, stumbling, etc.
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Old Jan 9, 2014 | 06:11 PM
  #24  
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From: Central Arkansas
Car: 1986 Trans Am
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Axle/Gears: 3.08? unlimited slip
Re: Quadrajet help

naf and paulo, I will try both of your suggestions tomorrow after the engine is cold. And paulo, that certainly sounds like that could be my problem.
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Old Jan 11, 2014 | 09:43 AM
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Re: Quadrajet help

Originally Posted by AssaulT/A
naf and paulo, I will try both of your suggestions tomorrow after the engine is cold. And paulo, that certainly sounds like that could be my problem.

So, how did it go? The choke pull-off was my guess as well, but I was trying to lead you through some diagnostic steps to get there. Many times it is easy to assume something and miss something easier because we assumed rather than checked. Most of the time, problems are caused by something simple.
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