In advance I would like to say that I am sorry for the length of my question. I have an '83 Ford Bronco with a 300ci straight six. Everything is stock. It starts fine, but while running at idle the engine will rev up and down. It starts at normal idle, starts sputtering until it almost stalls, then quickly revs up again, then sputters and revs up again and the cycle goes on as long as the engine is at idle. Once the engine idles for a couple of minutes the revs get farther and farther apart until it stalls. It is as if it keeps loading up, which is likely since the exhaust sprays out lots of carbon. My truck leaves a five foot spray of dark black carbon across the snow. There is no smoke though. I am almost positive the carb is dumping excess gas into the engine and have messed with the rich/lean screw at the base of the carb, but it doesn't affect anything. There is no change in idle. The truck has all of the pollution control stuff on it but none of it is hooked up. My smog pump is seized up and there is no catalytic converter and no pollution control sensors are hooked up, in case that is relevant. I just want to know why my truck has such an erratic idle and how to fix it. Any help would be greatly appreciated. Thanks.

 

Sounds like something in the carb is hosed - sticking needle valve maybe? Choice is either rebuild current or buy a new/reman carb. I would lean toward rebuilding - depending on the cost of the kit and how much you want to tear into the carb!!
Good luck at let us know how things turn out

 

Black smoke indicates you've got a rich fuel mixture. If attempting to adjust the idle mixture doesn't change anything then the problen is probably the float in the carb, needle vavles , plugged or some other internal problems. Time to either rebuild or have a remanufactured one put on. The surging could also be from a vacum leak, so check out your connections, lines, egr valve and gasket, intake/exhaust manifold bolts, and also check out how tight the carburetor is to the manifold. Any leaks around the carb can cause it to burn rich.

 

carburetor is to
>the manifold. Any leaks around
>the carb can cause it
>to burn rich.


Leaks will cause a lean mixture, not rich, Jonive.

Skipper, when did this start? Was it a progressive thing or sudden? I wonder if you may have old gas, dirty fuel filter, water in gas, Just aguessin'.

Good luck, Curti

 

check the choke. the choke doesn't just operate the plate on top of carb, it also operates the pulloff and ups the idle, and makes engine run richer!!! until warm. then it returns to normal if not malfunctioning. had same symptoms on old (yikes) blazer.

 

Thanks for the advice guys. I think that if I am looking towards a new/rebuilt carb that I will just wait until summer and buy a new intake and a four barrel carb. Until then I will check for vacuum leaks, all of the filters, and the egr valve to see if that helps a little. Thanks again.