How to fix an uneven idle on an Audi 80?

I've been experiencing an uneven idle on my Audi 80, where the engine seems to rev up and down without any control. I've checked the spark plugs, air filter, and fuel system, but still cannot find the cause. What can I do to fix this issue?

It's possible that your idle control valve may be clogged or malfunctioning. Simply cleaning or replacing the valve can often resolve this issue. I've had success with this method on my own Audi 80.