I have a 1994 sse bonniville I have a rough idle parked and while in gear at a stop light ,I have a 120 amp alt from auto zone could that be it

Doubt it'* the alternator.

Biggest causes of rough idle would be vacuum leaks or a well needed tune up. I'd start with the vacuum leaks.

This is done by visual inspection and moving each connector. Look for dry cracked or broken lines and replace them.

This is another good cause and fix for a poor idle:

http://www.bonnevilleclub.com/forum/...e=article&k=64

Are you getting a check engine light? If so, that'd be your first point of reference.

How old are the plugs and wires?

Must likey is plugs or spark plugs, but just for laugh look on the air filter. I had 94 corsica that would come close to stall because the air filter was really dirty .

Sounds like what I and a few other members here are experiencing. Is the idle fine until the engine starts coming up in temp, and then starts progressivly getting worse?

you said it lakevilleSSEi........ nice idle when cold.... good when warm in park or neutral. slight hiccupy idle in gear......

Mine idles rough once it'* about half way to op temp, and it'* probably worse in gear.

It all feels the same anymore....getting sick of it.

Nate...did you ever do gears and chain?

My '92 sse */c is basically like that too, and I've never found the cause.
It has plenty of power, starts right up, never stalls, gets decent fuel economy, and has no error codes, but usually idles a bit rough. The RPMs are steady at idle.
Mine, though, will idle rough on one day and idle much smoother the next day...same time of day, same ambient temperature, same distance traveled, same driver, same driving style, same traffic conditions. And sometimes it'll idle pretty smoothly as I come to a stop, and for the first couple of seconds after the stop, but the idle will slowly get more rough the longer it idles at a stop. The RPMs don't vary when that happens, and the boost gage reading is pretty steady. Kinda suggests a vacuum leak or sensor problem, but I've yet to find it!
I'm beginning to wonder if maybe part of the problem is the gas. I always use 91octane (this is the highest premium octane I've seen in my area), but California reportedly reformulates the gas at different times of the year.