I recently bought a 2007 S6 5.2L V10. When I start it in the morning, it has a very rough idle at 1200 RPM, for the first 60 seconds, then the RPMs drop to about 700 and it idles nice and smooth from then on. I've had it in for service at the Audi dealer. They did a carbon cleaning procedure on the valves and cleaned the injectors - neither of these things helped. Now they're telling me this is just "normal". The idle is so rough that I can't believe that it was designed to run this way when first started every day.

Has anyone had a similar experience and can tell me why this might be happening? The car is awesome except for this - I'm really hoping to get this figured out.

Thanks to anyone who can shed some light on this!

Matt

 

Well - for those 144 of you who have read this thread, I have an answer for you about the rough idle question.

It turns out that Audi has intentionally programmed the ECU to provide late ignition angles and an overly rich mixture until the catalytic converter reaches a certain operating temperature. During this time a secondary airflow is also provided at the exhaust valves which causes the excess (unburned) rich mixture to burn post-cylinder, promoting a rapid temperature rise in the catalytic converter in order to meet emissions requirements. This is all documented in Audi TSB: 2028344/1.

To prove that this wasn't just a load of hooey, I went to the dealership and started a cold S5 (2011) and an R8 (2012). In both cases, I saw behavior very similar to what I was experiencing in my S6. Elevated RPMs and a rough idle for about 45 to 60 seconds, after which time the RPMs dropped in a very controlled manner down to an idle RPM of 700 or so and then idled smoothly. Except the R8 which idles "smoothly" but doesn't let you forget the kind of horsepower you're sitting on :-).

I'm sure that certain conditions might exacerbate a cold start rough idle, but I am convinced that in my case at least, my concern is satisfactorily addressed. After 60 seconds, my idle is smooth as glass, and this controlled cold start idle is very consistent and reproducible every morning like clockwork.

The only thing that's surprising is that Audi would choose an approach that appears to make the engine "run poorly" for the first minute in the morning. Now that I understand what's going on, I'm fine with it, because I know it's not a defect, but intentional behavior.

So now you know. If this describes your car, relax - it's meant to be this way!

 

Yes my 08 A6 3.2 does this as well. It's like they programmed a "choke" mode where it idles higher upon first start to heat things up quicker. It's normal!

 

mrf2mrf thanks for the information. I was wondering the same thing but no one could tell me why, not even the dealer. guess I will educate them on my next stop.