I have a problem with my 2004 A6 3.0L (40,000 miles), The check light comes on, when it misfires when there is arough idle on start. The check engine light stays solid and illuminated for 1 week exactly, then goes off. It comes on again in a few days when Ihave a misfire with a rough start again, itstays on for exactly one week again. This cycle repeats .... So I took it to the dealer. The dealer re-set the computer and turned the light off and sent me on my way! In a few days it happened again. This time the dealer replaced the coil on Cyl #6, they said they got an error code pointing to that cylinder. I gotthe car back and it did it again within a day or two. They then replaced the ignition module for Cyl #6. I got the car back and it did it again in a day or two. They then replaced the spark plug on #6 (Why?, I do not know all the plugs were changedat the35,000 mile service earlier in the year!) I got the car back and when I started it a few hours later, the light came of again with a rough idle at start. I think the dealer is at the end of his rope!!! Each time I go in I get a new A6 loaner (very nice)and they get more confused. They have no idea... Anyone else have suggestions on what I should tell them to do. (This is all under warranty).

 

I had the same problem inmy 2002 A6 3.0 I hadton replace the coilm pack in cyl. #1 and #6 even though the skip started at cyl. #6

 

sory about the extra letters in some of my words I have mechanic hands

 

If it always happens on cold start i would recommend an engine decarbonization. Havent seen this issue with the 3.0 yet but it happened all the time with the 2.8. Carbon buildup would casue coldstart misfires.

 

Thanks guys for the messages. I am trying to convince the dealer to change all coils.

The idea of carbon build up is an interesting one. What would have caused carbon build up. It is low mileage, I change the oil with MobileOne every 5,000 and I use the highest premium gasoline. My commute is mostly highway. I baby this car!

What is the best way to clean the carbon build up?

Thanks again

 

There is actually a tech bullitin to replace all coils that are not up to a certain part number on the 3.0. Carbon buildup is caused by deposit from fuel burning. Gasonline is really just carbon, oxygen, and hydrogen. When it burns it can leave carbon residue behind. There is a kit that is used to run a cleaning agent thru the injectors to remove carbon buildup.

 

OK here we go again with the dealer...


The car has been in 4 times now with the check engine light and therough idle on start up. They keep clearing misfire codes P0300 and P0306 and have replaced one coil and the ignition module as well as a spark plug.
This week the enginestopped dead after half a turn. It did this twice in a 24 hr period..
At this pointI suggested they look at the crank position sensor, but they did not listen.
One other point last week I hadtwo morningswith a large cloud of smoke on start up. I had really odd smell, like an electrical acrid burning smelland smoke everywhere. Again they looked perplexed and disbelieving.

They now tell me it is likely the head gasket or a crack in the head. They have sent the head out for analysis!
Should I believe them??
I really believe that they have no idea what they are doing. I even helped them interpret the codes. This is a case where the counter guy knows nothing about cars and assigns the work to a new technician each time. (No kidding, that is what he told me) It is in the shop for the 5th long term stay in emergency care!!!

Yea they gave me a loaner, an A4 2.0 T. but I would prefer to have my baby back. I have nurtured this one from new.
Happy motoring
Derek