i just recently noticed that my 85 12a is idling rough what could be the problem. i just replaced the spark plugs and it is still doing it. does anyone know what the problem could be?

 

The problem could be a vacuum leak. Some recommend spraying carb cleaner around areas that are suspected as having a vacuum leak and the idle will increase when you hit the problem area. You do have to be careful though, carb cleaner is flammable.

It also wouldn't hurt to do a full tune up, and check your timing. A full tune up consists of new distributor cap, new plug wires, new fuel filter, new engine oil, new tranny fluid, new diff fluid, new coolant, etc etc..

 

I'm a bif fan of checking the resistance on the spark plugs wires.