I have a '72 Q-jet on a '73 motor. The engine will not stay running when cold without feeding a little bit of throttle for a minute or so. I moved the choke coil spring to "richer" and it seemed to improve a little, but still needed more fuel for a a minute or so. Turned the coil even richer for the next cold start and not much improvement. The problem is that the choke plate will not open fully when the engine is fully warmed, unless I do it manually. When I open the throttle even slightly, it closes the choke again and hence the idle speed is too fast. Could this be as simple as the choke coil being wound too tight, as well as maybe the fast idle screw adjusted too fast? I have worked on these carbs in the past(35 years ago) and am a little memory challenged concerning them. My Olds repair guide troubleshooting section did not help much. Any ideas? ( the carb is a fairly new rebuilt unit) Thanks, Chumley

 

You have essentially turned it too far and exceeded the limit in which the bimetal spring can open the choke when it's warm. Turn it back to where it was. To set the choke, just pump the gas 1 full stroke, start the car it will be in high idle. Let it run for about a min and tap the gas pedal and it should drop down a notch. Let it run for approximately 2 mins and then start to drive. If it's really cold idling for about 5mins will usually settle it down.

 

Thanks, I also have a Q-jet on my '72 Big block Chevy truck that has worked flawlessly since I put it on about 10 years ago. I have both original carbs from both vehicles. I think I'll get them out and fiddle with them to re-aquaint myself with the workings. Chumley

 

it sounds like you have the choke wound too far, and maybe your fast idle adjustment is incorrect. is the idle mixture set properly?


bill

 

Also, that choke if it is like my 72 has the tubes that draw hor air through the choke and heats the spring that expands it and releases the spring tension. Are the tubes hooked up and in good repair? If it isn't getting the hot air it might never get hot enough to release.