Watching the tach, it can't seem to stay put, but wanders a few rpm up or down at idle. It also sounds like it's missing randomly, and I can feel it shudder slightly when the rpm dips.

Should I check the spark plugs? Dirty throttle body?

 

How many RPM does it wander. It normally does wander a little bit but any variation of over 200RPM is too high IMO.

 

my dad's a6 does the same thing...any thoughts on what it could be?

 

when was the last time the fuel filter was replaced? Plugs?

 

There is a DIY on AUDIZINE I believe to clean the idle control valve on a 2.8. I'm going only by memory, but it's worth checking out,it's free.

 

Yes, my 1991 Passat di the same thing. Do a FULL tuneup, put in grea toil, clean out the idle motor, etc. Mine evened RIGHT out, and ran much smoother, to boot! Just my 2 cents. o2 sensor was geeting lazy, too!

Mike