I just rebuilt a 302 in my 79 f-150. I also rebuilt the motorcraft 2150 carb. It has been running absolutely perfect for 5 months. Now all of a sudden it won't idle. It starts fine, and goes down the road fine at all speeds, but you need to feather the accelerator when sitting still or it will die. Can anyone tell me why it did this all of a sudden, and how to fix it? I don't think it is a vaccum leak, i checked all the lines. Maybe the choke or adjustment screw?

flyhound

 

well whats thefast idle set at it should be set at 1,400 rpm is the choke working right what color are the spark plugs after it idles the 2150 carb is a very easy carb to master so it should be a easy fix.

 

Anyone else, that didn't help me much!

 

Maybe a piece of junk got through the filter or came loose inside the carb and is plugging the idle mixture screws. Have you tried the standard adjustments?

 

Well filter is brand new. If that was case wouldn't it effect it at other rpms also?

 

In order for me to help you i need answers like the plugs and fast idle settings!

 

i have the same problem as you ona 289 that i just put heads on. ihad to turn up the idle a bit so it would stay running at a stop

 

But it was was running fine, then bang, won't idle, i thought i was out of gas at first but that isn't the case.

 

Any recent backfires? Backfiring through a 2150 can blow the power valve and cause a rough idle. How about a vacuum leak? Maybe the engine is fine but the brake booster is shot?

Look at the plugs like ford390gashog said, too.

 

vacume leaks will make a carb hard to tune.you may need to retorque intake and the carb base after a rebuild.check for vacume leaks