What is the cause of my Audi 80's rough idling?

My Audi 80 has been idling roughly, what could be causing this issue?

The most common cause of rough idling in an Audi 80 is a dirty or faulty idle control valve. It is recommended to clean or replace the valve to see if it improves the idling.

Another possible cause could be a clogged fuel filter. Try replacing the fuel filter and see if it improves the idling.

Check for any vacuum leaks, as they can also cause rough idling. Replace any damaged vacuum hoses and see if the idling improves.