Generally the spark plugs and coil packs are the first thing you change when you get a missfire. They are known to go bad. As long as you dont have any carbon build up you should be good with just a fresh set of plugs and coil packs.
Engine light was flashing again this evening then went solid yellow as before. Taking her in to Audi tomorrow.
If it is plugs are they going to fanny around changing one at a time as they go wrong, or just do the lot. Hope their not milking me
Hmm, Audi said today there is still a misfire in cylinder 2. They changed the coil pack and plugs on that last week. They think it might be down to cold weather, and I need to leave car tomorrow so can try it first thing stone cold.
To be honest the car seems to have been fine up until this sudden very cold spell we’re having in the UK.
Finally I asked about the carbon issue, they said it does not happen to petrol cars and is only really a diesel thing so unlikely 
Wow what audi store are you going to?
carbon clean! Not a diesel thing, it’s a direct injection thing - now a feature with gasoline!
Also, unless they look pristine, don’t fiddle about with plugs n packs, just replace em all and get rid of the issue there, it’s not as hideously priced as I thought;
https://www.fcpeuro.com/products/audi-ignition-coil-service-kit-v10-s6-s8-ngk-06e905115e3
Fuel injectors also could probably use a service and clean - most definitely will if you carbon clean, but you might get away with just a fuel treatment. You’ve not mentioned injectors at all (have you?), so I’m going to assume you’ve got a less than ideal injector in #2… Swap it to another cylinder and see if the code follows it. If so - you’ve found the culprit?
So strange… on way home tonight I gave her a good ragging and engine light flicked on for just one for a second (while overtaking uphill again (why uphill the issue!)) then never again.
I then went later filled up with some high octane and ragged the living god out of her for half an hour solid.
No a single problem. No warning lights, no engine idle issues, zero - as if nothing had ever happened. It is milder weather today like 8+ now, it seems the old girl is a bit fragile on startup when its extremely cold (who isn’t ;D), but I found this on a forum today about the v10 5.2:
Rough Idle Answer
[i]I have an answer for you about the rough idle question.
It turns out that Audi has intentionally programmed the ECU to provide late ignition angles and an overly rich mixture until the catalytic converter reaches a certain operating temperature. During this time a secondary airflow is also provided at the exhaust valves which causes the excess (unburned) rich mixture to burn post-cylinder, promoting a rapid temperature rise in the catalytic converter in order to meet emissions requirements. This is all documented in Audi TSB: 2028344/1.
To prove that this wasn’t just a load of hooey, I went to the dealership and started a cold S5 (2011) and an R8 (2012). In both cases, I saw behavior very similar to what I was experiencing in my S6. Elevated RPMs and a rough idle for about 45 to 60 seconds, after which time the RPMs dropped in a very controlled manner down to an idle RPM of 700 or so and then idled smoothly. Except the R8 which idles “smoothly” but doesn’t let you forget the kind of horsepower you’re sitting on :-).
I’m sure that certain conditions might exacerbate a cold start rough idle, but I am convinced that in my case at least, my concern is satisfactorily addressed. After 60 seconds, my idle is smooth as glass, and this controlled cold start idle is very consistent and reproducible every morning like clockwork.
The only thing that’s surprising is that Audi would choose an approach that appears to make the engine “run poorly” for the first minute in the morning. Now that I understand what’s going on, I’m fine with it, because I know it’s not a defect, but intentional behavior.
So now you know. If this describes your car, relax - it’s meant to be this way![/i]
nothing like a good “Italian carburetor cleaning”!
Hopefully a good flogging cleared all that leftover caacaa outta the intake and cats too 
Thanks for the heads up! It’ll keep me from freaking out when the temps drop.
So, has been very cold here in UK minus 3 most nights and the old girl is struggling it seems as she has been fine up until this cold snap.
I started her up for a 20 mile trip to work today. Took it nice and easy for 15 mins until the temp gauge was where it should be. Here’s the crazy thing, I went to overtake not really a hardcore mashing but about 80% and I just new that as soon as it hit about 6000 rpm the engine warning light would come on - low and behold it did! It flashed on and off for a few seconds then went solid. Now normally when it does this it goes out and does not come back, but it seems this time its back for good - for the whole journey there and back when I started the car some hours later.
Anyways… guess I’m gunna have to eat some humble manifold pie shortly, it will be interesting to see when this weather lifts this issue goes away.
Do you have anything to pull codes with? VagCom is a tough pill to swallow at $600, but I got a Carista and while really limited at changing features, it was perfect to list all the current codes stored. Apparently they updated their hardware to work with other apps. $40 for the Bluetooth dongle and another $40 for a years’ worth of in app, unlimited feature unlocks (which is horseshit!), it’s a cheap(er) alternative to pull codes.
Hi,
Quick update. Seem to have it ‘fixed’ for now. Took motor into ATS. guys very helpful and said exhaust was a bit blowy with two tiny holes so welded up for me.
At same time ran VAG and said me good old No.2 injector is an issue and is whats causing engine light to come on. So ran some engine cleaner stuff through her on a full tank etc then cleared down codes. Ragged the living b’jesus out of her and not a single issue - feels right as rain
The only thing I would day is weather is mild now, so real test will be next cold spell. My take home during all of this is: get second opinions other than the Audi service, and don’t boot the old girl when she’s stone cold… obvious really… but will nurse her bit more in future when cold.
Cold starts with the SAI on make the car run like crap. so its best to just let it warm up before you give it a go. Also it helps keep the carbon down if you start and drive the car not letting it sit and warm up.
Injectors are one of the silent issues on these cars. I think almost everyone has had one injector that is bad has gone bad or is going bad.
Good update. Thanks for keeping us informed.