I jusr had a friend rebuild my quadrajet carb. (Engine is a 350), When we trying to set the timimg I pushed down on the gas and when I let up, the engine continued to run at the same rpm. The throttle spring could not pull back the throttle. I can't get the throttle to stick with the engine off. Action of the linkage and accelerator cable seems fine. Something in the carb, only when the engine is on, is causing the throttle resistance to jump way up. When the engine is running I can rev the engine by pushing on the throttle plate and you can really feel the increase in resistance. Any clues? was there a mistake in the rebuild?

Thanks

check the throttle shaft it could be bent or the area it rides through dunno if there are bushing in the body or not