I have a rebuilt Motorcraft carb on my F100 302, starts and runs like a dream. I pump it to make the choke set so it will be on high idle and such. I let it run like that about 10-15 seconds and then kick it down to curb idle. Idles fine on curb idle but sometimes I cant get it to come off of curb idle. I was wondering if maybe it is a thermostat problem(maybe stuck open) and the engine isnt getting to the temp it needs to be so you can get the curb idle to kick off to regular idle. The temp guage barely gets to the normal mark and seems like it takes a while. I don't know if the guage is acurate though. It seems like if I drive it first and it gets a little warmer then I put it in park and hit the gas then it goes to regular idle.

 

Is the step cam hanging up on the fast idle screw?

 

Hmm dunno... I will have to check tomorrow and see if that is the problem.

 

Curb idle is regular idle.

There are only two idle stages: The fast idle, and the curb idle.

If you set the fast idle too high, the screw may be hanging on the fast idle cam. Or the choke pulloff isn't correctly adjusted. Or the choke is not operating properly.

 

Ok I will check that. I figured the choke is working properly since it will crank right up at the touch of the key(the engine never turns a complete revolution, which ever piston is up ready to fire it starts).

 

I looked today and don't see anything that is catching it. Choke is fully open when the engine is warm. I clicked off high idle this morning and it went all the way down to regular idle like its supposed to but it don't do it everytime.