Did you check the hose for any cracks?
What about the timing on bank 2?
Oily coil pack tips?
At first I’d check the compression ratio on bank 2 and use a camera to get a picture of the cylinder walls. Don’t be like me chasing a problem and spending 11k euros before doing that. It can safe time and money!
Other than that it might be the injectors leaking. Yes they fail a lot and I’d replace all 10 of them at once. If one fails the 9 Other ones will fail shortly after that.
I’ll do that and report back. What is the fix for peeling cyl liners?
Unfortunately a new engine or at least a new block with pistons and heads. I mean that would be the worst case and let’s not hope that it is the case but better be safe and check it too. An overhauled good engine with installation costs around 6k here in Germany or get a used one but always ask for photos of the cylinders and compression stats.
Here are some pics, but i don’t really know what to look for. However, the spark plugs don’t look great. They were last changed in 2016, 40K km ago.
Cyl 6
Cyl 7
Cyl 2 - does NOT misfire
We need to go deeper into the cylinder to see possible damage however 40k km is way too much for these spark plugs in my experience. I’d try changing them and maybe the misfires are gone. Since they already look that bad I’d start with that.
I can’t click on the pictures to have them in a larger format.
40.000 km is quite a lot for a set of spark plugs. But why do you think they look bad ? I’m thinking of the one from cylinder n°2, looks fine to me. Grey-ish/white-ish color is a good tint. However, if the procelain started to melt, ain’t good, means you’re running poor.
From what I’ve been experiencing on mine and after talking to some other enthusiasts the lifespan of a set of sparkplugs is around 25k km max and not longer than 2 years. The V10 eats sparkplugs and coils like it’s nothing.
From what I’ve heard and been told, I agree with you even though I base myself on max 30.000 km or 4 years.
I bought an S8 on june 2021 and got some intake issues last december. Surprise… coils AND spark plugs were the ones from factory (got pictures), car is from october 08’, 169.000 km ! No cells nor misfire during my short (for now) ownership. I am still confused about it.
In my experience the harder you drive it the sooner they’ll just die. I own it for 2 years now and every time in summer at least one coil or plug dies on me. I always carry spare plugs and coils with me. But he should definitely try changing them with NGK plugs. Yes they’re 15€ a piece but I can only praise them.
cyl2 is one of the few cyls that are NOT getting misfires. usually it’s cyl1 and 6-10 acting badly.
What I discovered is that a simple restart (e.g. “reboot the ECU”) seems to fix the rough idle––until the next time. I had thought the plugs were on a 40K mile replacement schedule, but they are easy enough to replace.
If plugs & coil packs are all that is keeping me from smooth sailing, then I’m all over that. However, the random/intermittent nature of the misfires, and the fact that a restart seems to temporarily fix the problem, has me worried it is something else. Am I wrong to be concerned?
Have your injectors been replaced yet? I mean I’d start from the “cheapest” solution and work my way up. I’d change the plugs drive it for some days or so and watch the car carefully if it’s gone than thank God if not then the coils, then the injectors. Has the PCV system been checked yet?
Injectors were flow checked and a few replaced at the same time as the spark plugs in 2016. I have also recently replaced the oil separator and the hoses that go into that unit all seem solid. But I haven’t been able to find a place to do a complete vacuum check.
I think I’m gonna swap plugs from cyl2 and 7 and see if the misfires move to 2.
If you want to see bigger photos from above, find them here:
cyl 2 (GOOD): https://postimg.cc/gallery/gnCj9Bg
cyl6: https://postimg.cc/gallery/FLJx8JR
cyl7: https://postimg.cc/gallery/yB9jB0N
Yes that would be the first thing to try if it moves then you know for sure it’s the plugs.
5-6 years should be good for injectors however my 06 Avant now has it’s third set of injectors in it since one failed during an autobahn drive. Everything is plausible with these.
Yes. Without overreading the plugs, the one on cylinder 2 looks ok, the other two look like past their prime (see the white-ish little spots growing on the porcelain and/or electrodes). I’d start by installing 10 brand new, good quality plugs as bad plugs overstress the whole system. It is also quite cheap.
Good news is that you’re not running rich nor poor !
Swapped plugs and coils for cyl 2 & 7—but the misfires stayed with 7. What does that say, check the injectors? Should I change plugs and coil packs regardless?
On what cylinders do you have new injectors?
And are the new injectors with stainless filters or plastics?
I replaced 4 injectors before I realized that the only problem with the original ones were the plastic filters causing misfires as they degrade.
So I now run on original 2006 injectors on 6 of the cylinders with no problems ( I removed what was left of the filters)
Car is nearly at 250.000 km
In Denmark thats just about “break-in” mileage 
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Aren’t you that sick guy who managed to get 500HP from that V10? Haha
From what I can tell is that usually all will go bad in short time apart. So if one is dead it’s better to change all of them.
I’d say he should maybe check compression on bank 2 entirely. Doesn’t take a lot of time.
That might be me, yes. But that’s on the last tune 
JHM’s wizard has been doing his magic again 
For me I just did what I mentioned above.
In general I would also advise to change all injectors, or just the older ones.
Same with PCV etc.