I have a 1985 12A engine w/ stock carb, and it has an idle problem that is bugging me. The car idles pretty smoothly at 800 rpm when it's hot, but misses about once every 15-20 seconds. If I hit the throttle to above 2500 rpm or so and let up, it misses horribly as it approaches idle around 1200, but then smoothes out when it gets to 800. As long as it's not in the idle circuit, it has no noticeable miss. The spark plugs are clean, the timing is dead stock. Also, when the engine is cold, it idles very low, like 300-500 and barely holds it. When it's choked it runs badly as well.

I just recently got the car, so maybe all these are normal? The only thing I can think of from looking at the manual is maybe shutter valve or coasting valve?

Thanks.

 

It sounds like your idle fuel mixture is off, though I'm fairly new to this too, so I'm not sure, but to me the mixture needs to be richen up a bit, maybe someone else would have more info.

 

kinda sounds normal to me mine makes studers with little pops everytime i let off the gas and when its cold mine idles low and with choke it sounds nasty but normal for the most part unless i hold the choke with gas then push choke in and let of gas.... then i lay backfires but only does this when its cold..lol

 

I would start with ignition just to rule it out.
Could be a couple things with the carb, so eliminate the variables of spark first, IMO.
New plaugs, timing, be sure the trailing is firing when it should, etc.