This one is on a 302 in a '73 F-100. Over the last few weeks I've noticed that after warming up, and when stopped at a light or stop sign, or after starting the engine again when it's warm, the idle speed will climb too high, to the point of banging into gear when shifting the C4. I noticed however, that if I kicked the throttle a few times, it would 'sometimes' go back to normal idle speed. So I tried resetting the idle speed screw at the throttle lever, but even at the point where the screw was OFF the lever, it still idled fast. I had checked the setting of the idle mixture screws before this started, and they were okay. So I pulled the accellerator rod and return spring off, to see if I could feel a catch somewhere (like the butterflies might be catching in the bores maybe). This was smooth, so I pulled the carb and visually noticed that the butterflies were not closing all the way. They only stick open a tad more then when they'd be set at normal idle, but that could be enough. Couldn't figure out why. Then I noticed that if I held the choke wide open, the butterflies would close all the way! The choke has always seemed to work fine.

So, is it possible that some misadjustment in the choke might be causing the butterflies not to close all the way to proper idle? Does that make any sense?
The choke seems to open fine when warmed up.

 

It's definetly hanging up on the fast idle cam. Do you have the hot air choke or an electric choke?

 

Electric choke. I did check that setting and it seemed okay, and nothing's gummed up. I may not have checked it correctly however.

 

With the engine running, pull the wire off the choke and check the voltage. I'm probably wrong (A little rusty), but I think it's in the 6v range if you still have it plugged into the stator terminal on the alternator.
If you are having charging problems, this could be causing the choke to not open fully, or the choke coil may be worn out.