I have a 96 Monte that is my daily driver with 113k miles on it. It has an intermittent rough idle about every other day with no engine codes. Where should I start looking for the problem? It does make a sound when it idles rough and i can best describe it as a "woom woom woom woom" lol

 

I'd start with a tune up - replacing spark plugs, wires, fuel filter, air filter, etc if it's not been done in recent memory.

 

I'd start by reading the sensors to see what data you can gather from that. Even if there are no stored codes, it can be helpful to understand what the pcm is seeing, especially the cylinder misfire counts.