My A4 3.0 has a bit of a ruff idle when I come to a stop. The idle comes back up and runs smooth until the next stop. Last month I replaced 4 coil packs and 6 new plugs. I got better millage but the ruff idle is still there. I have read other comments about coil packs or a vacuum leak. Last year I installed the Hyperflow intake, which is a K/N type air filter. I seemed to notice this issue after I installed it but was not sure if I had the problem all the time. I did check to see if the original air box had a vacuum assist that would need to be plugged but no luck.

Any suggestions what I might look for? Should I carry a few coil pack in my trunk?

 

i keep spare coil packs in my trunk. 8 actually. i have 4 hitachi e's and 4 of the standard ones that you get from audi

 

Things to check:

Dirty MAF
Clogged fuel filter
Dirty throttle body
Check the air filter and breather system for any obstructions
Faulty sensor SOMEWHERE. Audis have tons of them
Run a scan and see what faults come up

 

^^^
and a cracked snub mount