nortsnorts

I have a 2009 A8L 4.2 with 25K miles that runs flawlessly except for a rough engine when cold. Sometimes it will hesitate, shudder and chug at stop lights until the engine warms up and then all is fine.

The local dealer has checked for codes and nothing comes up. I did have the fuel pressure sensor replaced about a month ago when the ECU came on suddenly and the car almost died, but the rough engine issue started before that and still persists.

I called Audi to complain and it was suggested that I take the car to another dealer to see if they have better success...this doesn't sound promising to me.

Has anyone else experienced this and/or found a solution?

Vicl

Why do not you suggest them to start from replacing sparkplugs? Years ago on my old Audi V8 I had something like that. The issue disappeared as soon as I’ve replaced the sparkplugs.

jakematic

Spark plugs sounds plausible, but you're at a really low mileage.

Have you checked for outstanding TSB's for the coils, etc ? http://www.audiusa.com/us/brand/en/o...in_lookup.html

Brozee

This happens every single time? Or was it just one rough start. After owning my A8 for over a year and a half as my daily driver. I only had trouble starting it one time. It was after it sat for two days in the frigid cold, just kept trying and trying and it finally caught and revved up. If it happens every single time I mean my guess would be the plugs or even the coils like the previous poster said. The dealer will work it out for you. It's a new car there's no reason for you to even need to post on the forums for issues with it if it's still under warranty. Dang you audi!

s4master1

There's no point giving suggestions as they will not get you anywhere.
a local dealer send us one with similar issues, hard to start in the morning specially when cold, rough idle at take off hesitation and throttle delay.
after inserting a camera thru the throttle flap we saw large amounts of carbon build-up, once cleaned all those concern were gone.
however this does not mean is your case and don't take this as a suggestion,

you will find very little helpful information here specially because your car is FSI and most owners here don't have that, I suggest you cruise the RS4 forum.

Edd W

Where does the carbon build up exactly?
We have had Fsi for a few years longer than is the US and there do not seem to be any of the same issues here - our fuel must be a different blend?

s4master1

Accumulates in the intake runner flaps and the intake valves.
definitely better gasoline in Europe, specially compared to So Cal gasoline.

s4master1

Here's some more

s4master1

Here's some more

Edd W

I take it that inlet valve has been cleaned up?
On the Fsi, why would it build up like that when the fuel is injected directly and nothing goes in the inlet tract?
Unless it is the pollution in the air drawn in and deposited on the first surface it hits at speed. This could be emissions from the exhaust of other cars picked up by the intake. If so, I guess US driving styles are different as well causing this to happen and not in Europe?