Yet another CIS issue
 

My 1980 SC is bucking between 2200 and 2500 rpm. From research on the board, this is caused by a mixture problem, too lean or too rich. I've done a good search on the forum for CIS related questions and answers. I found the thread where souk walks through an adjustment without the benifit of an analyzer. I am working on trying to use his method, but I haven't got to the point on the too rich side to cause the engine to stumble or cough. I can take it too lean to stumble, but when I try to go to the rich side, the idle starts to increase dramatically. Am I not going far enough? The bucking seems limited to between 22-2500 rpm. Here is another question, I am supposed to track the car in a DE event this weekend. If the bucking persists as I described, am I placing the engine in danger by running too lean and damaging valves or pistons?
Thanks,
Jim S.

This may be an ignition issue. But it's always good to make sure your fuel adjustment is correct. Try disconnecting the advance and retard vacuum line (one at a time). Plug the vaciim line with a golf tee. If the behavior changes, you may need a new vacuum pot.

Having been through the biggest whopper of a CIS overhaul at late, I completely agree with Souk. Pull and test each plug wire with a OHM meter, check the coil, cap and rotor as well. Make sure all of the wires are "clicked" into place when attached. This really seems ignition realted.

I agree with Souk, and in particular, it may have to do with your distributor's advance mechanism. How are the bushings in it? If you remove the dizzy, do you get a noticeable amount of axial play in the distributor shaft? If you pull the advance vacuum line off it and suck on it, do you see the dizzy plate advance smoothly?

ianc