GTO Choking on Idle - Pontiac GTO Forum
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post #1 of 4 (permalink) Old 05-12-2019, 01:29 AM Thread Starter
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GTO Choking on Idle


I am admittedly new to working on my own car, so please be gentle. I have a 67 GTO with a new Edelbrock carb on the 400 and the stock his/hers shifter (for now).

I am having a serious issue with idle where the car will idle at different speeds for no apparent reason, and eventually, the engine will begin to shudder and eventually die. When I give it gas or open the throttle at all while not moving, it seems to help, but the car is clearly choking out. She has only ever done this moving between lights. This has never happened to me when I turn it on and let it idle without driving. After checking electrical wires and the electric choke I have on it, I went and tried to open up the carb a little. None of it really helped and I am still getting the different idle speeds.

Can anyone give me some pointers about what to look for and what might be causing this?

Alternatively, does anyone know of any reputable engine guys in the LA area that I might be able to take this to?
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post #2 of 4 (permalink) Old 05-12-2019, 08:04 AM
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I would look for vacuum leaks, sounds like the vacuum advance on the distributor may not be working,

Good luck,


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post #3 of 4 (permalink) Old 05-12-2019, 09:58 AM
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Could be a couple things.

Which Edlebrock carb? Q-jet or AFB, and which model number?
Which intake? Stock 1967 Q-jet? Aftermarket?

If I had to guess, the symptoms sound like a carb that is flooding - raw gas is entering the intake. Maybe the float is set too high? But, read my next guess.

Second, the choke is not operating correctly. Make sure it is fully open. I assume the weather in CA is not too cold, so your choke should open up fairly quickly. It may be adjusted too tight and without enough air entering the carb, it will also act as if the carb is flooding. Did you test the wire going to the electric choke for power?

Being new to working on the car, is your idle set high enough?, idle mixture screws adjusted correctly?, did you use the correct carb-to-intake gasket if original 1967 Q-jet intake?, and as 05GTO, it could be a vacuum leak or an ignition problem.

Start at the carb. Check for vacuum leaks. Then check timing.
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post #4 of 4 (permalink) Old 05-13-2019, 07:30 AM
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Agree with the gang,...would also add..

1).....”New” carb
2)...stalls under load (while trying to drive not idle
3) “Opened up the carb a bit”

I would try to reset the idle mixture from the beginning on th mixture screws and pay attention to your idle rpm. At this point make sure that since you can idle the car get it warmed up to temperature and just make sure the choke is fully opened and not playing a role.

Set the idle mixture screws per the carb’s instructions you know 1 1/2 turns out etc. the throttle screw cannot be opened too much only slightly or your idle mixture, which runs the car from 0 to about 2500 RPM’s will be off.

Of course as mentioned vacumn leaks and timing could be factors, but since the carb is new....reverify your work there..

As PJ said tight carb base gasket, and do not over may get it so it is easy to drive and you can take it to a shop you find easier.

Good luck you will get it,..sounds like minor adjustments needed.
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