How many miles does it have on the clock and what sort of motoring have you been doing?

 

Thanks Gary
It's only done 23000 miles and I was pushing it hard but normally it's just normal motorway/A road commute.
Thought it was fixed but it misfired again today as I gave it the beans , it's possible it was just the limiter kicking in but I don't think so. The garage are a bit stumped as to the cause and are contacting the Audi technical dept. Any insight would be great.

 

Fuel should be injected as the finest of sprays - If this is not the case, not all the quantity of fuel that is injected will have time to burn fully, thus leaving sooty deposits: A certain level of sooty deposit is considered normal for a tfsi engine.

A difference in colour between the deposits on the injector, similarly to the colour of deposits on a spark plug, tend to indicate differences in the air/fuel ratio - lighter ones = more air - sooty ones, a higher ratio of fuel. The idea is to get the manufacturer's balance. Thus the lighter one seems to higher ratio of air / a lower ratio of fuel.

(At this stage, it would probably be wise to look at the state of the spark plugs in each cylinder - is the pattern of deposit on the outer ring and/or the ceramic insulator comparable with the state of the deposits on their respective injectors? I assume that the garage has inspected the plugs.)

A greater ratio of air would indicate that either (i) the other three (the sooty/black ones) are equally starved of air - which seems unlikely, or (ii) the lighter one is injecting less fuel - a fault in the injector caused by a restriction, lower pressure, and/or an air-leak.

You could cross your fingers and try a few doses of "injector cleaner"

Dirty injectors from a tsfi engine (not a TT): you will see that there isn't much difference in the colour of the deposit.

This problem seems inevitable on direct injection engines.

 

So after much scratching of heads at the dealership and several phone calls by them to the Audi technical help desk the problem has been resolved. It turns out that there are two fuel pressure sensors in the rail for the fuel injectors, one big one which the garage knew about and a small one they didn't know about (considered getting them a Haynes manual) which was the one causing the misfire on hard acceleration. Took them a week to work this out but got free lifeshine,first service free and use of a new TTS for a week.
Took the car out for a run tonight and now I'm all grin.

 

Ok are you sitting comfortably?
Then I'll begin.
Once upon a time I bought a 2011 TT convertible, it was black and shiny and I couldn't resist so I paid the dealer the money and took it home to show off to my family and friends.
Then on the last warm day of the year I drove to Halfords to get polish for my new car, top down it was great.
Parked the car ,bought polish then got in the car which started and then died!
Audi rescue arrives and I get towed back to the dealership, I am not a happy man!
Two days pass and I'm told it's fixed after needing a new fuel pump and sender unit.
Next day the misfire appears!
Returned to dealership three more times , they have replace plugs,coil packs, Maf, injectors and fuel pressure sender unit.
It still misfires and is in fact now worse than ever!
In the two months I have owned it the dealership have had it more days than I have and they cannot fix it.
I have now given up and returned it for an exchange on a newer 2013 coupe in volcano red.
It's a late 2013 car with tech pack.
Fingers crossed this one will deliver.

 

Crank sensor problem maybe causes engine misfire then shutdown

 

This is such a helpful response, on a 7.5 year old thread 🤦‍♂️ 🤦‍♂️ 🤦‍♂️