Audi A6 3.0t Misfire on Cylinder 5 Caused by leaking piston rings

[cdzim]

I recently bought a 2011 Audi A6 3.0 with a misfire on cylinder 5, and it having only 25 psi compression. On farther inspection, by removing the head, I found the piston rings to be leaking oil, with a scratch in the cylinder wall. Is this a common issue with these engines? I couldn't find much on cars that didn't have a lot of mods.
20230717_205003.jpg

[King_Tutt]

That is not common, they tend to burn or leak some oil. Depending on maintenance and oil used you will see higher or lower consumption levels.
However from the picture it looks like cylinder 5 sucked something in causing the vertical scratch, how much carbon build up was there? Any recently done maintenance on the car?

[cdzim]

I will try to get a picture of the carbon build up on the valves in a few days. However, I have included a picture of the pistons. When I received the car, the intake filter was removed, and the engine was getting unfiltered air. I do not know how long it was like that.
IMG-20230717-WA0010.jpg
I do not know the maintenance history of the engine. I plan to replace the rings on that cylinder and hone the cylinder to remove some of the scratch with this tool. Do you see any problems with this approach? The engine has 104k miles on it. It was running and driving, with a misfire on cylinder 5. If I can fix the misfire, I will consider that a win, even if it burns some oil.

[arjun90]

This is why it is important to walnut blast. Most previous owners likely never meticulously maintained their vehicles. I just recently did an engine oil flush on my A6 3.0T - the difference was night and day, even fixed oil consumption issues to a great extent.