Throttle sticks only when running

[86454]

Quadrajet 17085212 just rebuilt with SR kit and new primary shaft bushings.  The throttle returns fine when truck is not running but with it running it doesn't.  I can have it running at 1500 rpm with the stuck throttle, shut it off and it returns to the idle position. There is a huge difference in the torque needed to turn the primary shaft when the engine is running. I know engine vacuum will cause some but this is a 270k mile 454. I have tried a bigger return spring and it does help but still wont return to idle. I am afraid too much spring will bind the shaft.

Any ideas? I am just stumped.

[86454]

So far I have tried the following with no improvement

unhook accel cable
remove accel pump lever
unhook electric choke and wired it open
unhook and plug vacuum line one at a time
cussed out the carb
verbal berated the carb  and threatened it with replacement

Could it be something to do with the engine and not the carb at all?

[Cliff Ruggles]

Does the shaft turn freely in the throttle body after the bushing installation?

Clearance between the link that operates the secondaries and the arm on the secondary shaft.

Throttle plates indexed, centered and completely sealed off when closed (all four of them)?.....Cliff

[86454]

I know the shaft turned freely after I did the bushings. I will have to pull the carb to check on the other two. Darn, I just had it off to plug that gasket hole behind the secondaries.  Thanks

[86454]

A little plate adjusting,a little rod bending, a couple drops of oil, and a bigger spring seems to have done the trick.

So basically all of the above (to Cliff's response) needed attention.

Now it's time to search the forum for solutions to my other carb issues.

Thanks!!