lumpydo

Ok, I have a 2006 A4 S-type quattro with a 6 speed auto. When it idols, it sounds almost like a newer diesel. When I'm driving it, I hear a gravelly sound. If I'm on the gas heavy its OK. If I'm not on the gas, its OK. It's under light loads that it makes the noise. Not sure if both noises are related or not. Don't think it's a hole in the exhaust. Could it be a bad cat?

I also had a CEL on. We checked the codes and I got a bunch of misfires.

A4Audi4Fun

2.0 FSI engine does sound diesel like at idle - it's the high pressure direct injection fuel system at work. See if you can find another Audi on the street and ask to hear what that one sounds like at idle or ask a friendly dealer to listen to one of the cars they have on the lot.

lumpydo

Thanks. I tried to listen again at my neighbors 2.0 GTI fuguring it was the same engine.

Also, I updated this post about a CEL. What do you make of that? My buddy thought it was the crankcase breather valve or some other vacuum leak. I sprayed it with carb cleaner while it was on and the engine was running. It sounded better while I was doing that.
Tried to take it off and clean it, but its still idoling poorly.

Prospeeder

While its running, try and remove the oil cap. If it comes off easy the vent is fine. If you cant take the cap off or its super difficult the vent it stuck open and putting full vacuum on the crankcase. You just need to replace the crank vent, they are cheap.

lumpydo

I'll give that a shot. Thank you

Highmile

Take it apart, I bet your cam follower is badly worn/ destroyed. If so, it is flinging around bits of metal, so take it apart and fix the issue before more damage is done.