change fuel filter under the driver side bolted to the frame
yes mine had a really rough idle and it turns out the motor mount needed replacing
There are many things that can cause a rough idle on this car. The computer could be going out, the engine may not have enough oil, and the engine may not be getting enough fuel or electricity.
Check the motor mounts.
Try checking your spark plugs & wires. Can also be caused by dirty fuel filter.
In old Chevy's it was vapor lock, which is the fuel boiling in the fuel lines. You can try to insulate your fuel lines and check fuel pressure..Could also be bad plugs.
vacuum leak?
Could be the auto idle control valve, try cleaning before replacing (about $300). Another simpler possibility is the fuel filter,replace this first,
The Chevy 4.3 egr system is important to the proper operation of the engine. A clogged egr can cause rough idle or low fuel economy, among other things.
Rough idle on a 99 Dodge Stratus is often caused by a clogged fuel filter or injectors. This prevents the engine from receiving enough fuel when needed.
The engine of a Chevy Trailblazer may begin shaking when idle if there is insufficient fuel reaching it. This can be caused by a clogged fuel filter or dirty fuel injectors.
Fuel injectors
a pile of poo