Pontiac 400 Idles to fast
I need some ideas on this problem. According to the tach the engine is idling at 2000 rpm. The tach is good as the engine is roaring at idle. The throttle plate is fully closed and there is a gap between the idle speed screw and throttle stop. Moving the fast idle cam does not help. The idle mixture and fast idle mixture screws are set at 4 turns out. It's a 700 cfm 4 barrel Q-jet. I haven't done any internal work on the carb.
What should I try next?