hsp

Recently car starts/idles really rough when cold. MIL light turned on. After warm up or quick blip of the throttle, everything back to normal. Carbon buildup? Spark plugs? BTW, 2007 S6.

Midwestuser1

Carbon build up is very possible if you've never had a manual cleaning.

slicksic

Had the same problem for a while now as well.
Had manual cleaning done, replaced high pressure fuel pump, fuel filter, intake manifold and spark plugs.
Problem still there. When you blip the throttle and the problem goes away would make you think that carbon build up is not the issue.
What is the code for the check engine?
My next guess is that fuel injectors are leaking into the cylinders while the engine is sitting, and once you blip the throttle or let it run, it burns itself off.
Please get back with check engine code and let us know if you ever solve the problem.

Lazydog

Has this just started since the morning have gotten colder or has this always been there? Reason I ask is I know of no car that will run like a champ on starting until the motor starts to warm up.

As to this being a carbon issue I can tell you that I still have the rough idle on cold morning even after having the carbon cleaning done. My idle issue only started sinc eit start getting cooler/colder in the mornings.

https://www.audiworld.com/forums/sho....php?t=2832476

hsp

Indie states misfire code on cylinders 5 & 9 but cant explain why problem goes away after engine warm up or blip of throttle. Outside of this issue, the car runs like a champ. Hate to spend big bucks for manual intake cleaning if this wont solve the issue. Dont know where to go next.

slicksic

Does the problem go away/diminish if you leave the key in the ON position for a few minutes before starting it? Try this and please report back, this may be a clue to help your indie solve the problem.
I have the same issue as you and I know when I do this the problem is usually a lot better or even not there. Not sure what the explanation would be though...

hsp

Problem went away on its own?!?! MIL light turned off and engine running a lot smoother at cold start. I have no idea what happened, but happy with result.

Hope it doesn't rear its ugly head again.

J. Patterson

Our 3.2 was doing this. Extended crank time when stone cold, idled a bit rough and engine rpms fluctuated at idle and light throttle till warm. I expected that it needed intake cleaning but it turned out to be a small vacuum line from the intake flap servo motor that had a split in it. Dealer found it and I was impressed.

cebo0650

Mine is at the dealer today for rough start/idle. Did not see a MIL but scanned with VAG and show s number of cylinder misfires logged.

I requested they do the manual carbon cleaning. Can't wait to get it back and see the improvement.

I have just over 100K km on the odometer, but my trips to and from work are very short (just under 4km) so these are the worst possible conditions when it comes to carbon buildup.

ericA6

How much are they charging you?