VW Tiguan 2012 132kW TSI 6sp manual - misfire problem

[TMac]

Hi VW mind trust,
I have been told a "I don't know" by my mechanic and so I thought I would ask the VW team to see what you think...

The current problem is intermittent and seems to be a misfire on cylinder 2. About 11k ago there was a similar problem and the spark plugs were changed and ignition coil replaced for cylinder 2. Problem seemed to be solved.

On Sunday a week ago my Tig suddenly was running rough with the engine light coming on - misfire felt like it was back. The engine light was on and blinked once about 2 times, and EPC came on for a bit, no smoke visible, but power dropped like last time so was 99% sure misfire. About 10km after coming on the rough running seemed to stop (was limping home). When I drove to the mechanic on Monday morning the problem seemed to have gone. Conveniently whilst at the mechanic the problem reappeared and they got a similar misfire on cylinder 2 again. Apparently the spark plug came out a bit wet. The problem seems to have gone, but I think it might come back. Mechanic said they are unsure of the problem.

I will get some history of what has been fixed in the car over the journey but I am pretty sure the fuel pump was done about 170k.

Let me know what you think might be a cause of the problem. Any suggested VW mechanics in the Manly area? Is getting a carbon clean (walnut blast) something worth considering?

Here is a bit more about the car (not sure if useful or if more info is required just ask and I will add).

Tiguan 2012 132kW 6sp manual.
I have owned since about 50k and now up to 211k km - bought in late 2017.
Tend to drive a fair bit for work so up to 1000km a week with most being on the freeway up to Newcastle.
Tends to use a bit of oil, which seems to be common, and I think about 1L about every 2000km.
Doesn't blow smoke and fuel consumption is very consistent (680-740km per tank). Have been using E10 usually, although mechanic suggested using 98 more often (tend to put a tank through occasionally prior to this).
Have noticed a zzzzzz / clicking noise when off the coming off power and idling with gears engaged (to try to describe the sounds as when not pedaling a push bike the clicking noise you get from the rear cluster sounds no dissimilar - since only when no power I was assuming this is a normal sound).
The engine light has occasionally come one over the last 100kM. I have usually assumed this was due to the emissions being out of spec due to the fuel and haven't worried too much. Has nearly always gone away on the next fuel tank fill. Occasionally have had a bit of a drop in power, but as hasn't lasted I have assumed injector, or similar, briefly blocked and problem gone.
I am wondering if any of the above is related and thus have put it down if this helps.

Been getting the car serviced a Balgowlah Automotive (Sydney) regularly which I think have been good and are close to home.
Car is in pretty good knick for the age and I like the manual so at this point (and with high costs for used cars at the moment) am keen to keep it (go for 300k km?) but don't want it to become unreliable or a money pit.

[Lucas_R]

With those km's on the 2.0TSI engine you likely have carbon buildup on the intake valves starting to become an issue and causing misfires.

The 2.0TSI engine in your car is a direct injection engine so the fuel is injected directly into the cylinder chamber, and therefore does not wash over the intake valves to keep them clean like a traditional port injection engine does. Over time the intake valves become dirty and slowly get clogged up with carbon until they no longer can seat properly to allow proper compression - which not only causes a misfire but reduces the engine power. All of this happens very slowly over time so you are likely to not notice the drop in engine power.

You should really only be using 95 or 98 octane fuel (not E10) but its your car so you can do what you like.

Assuming its not your spark plugs or ignition coils causing the issue - then its likely to be carbon buildup.

You can buy products at Supercheap / Repco to do a basic DIY clean which you might need to do 4 or 5 times to get a reasonable result, otherwise the only proper way to fix it is to pay someone to remove the intake manifold, and clean the intake valves with either a walnut blasting tool or manually using picks and sprays to help soften / loosen the carbon buildup = $1000+

Liqui-Moly Petrol Engine Intake Decarb - 366g | Supercheap Auto

In addition, the injectors themselves are likely to be clogged with gunk, so buy a good quality injector cleaner and put that in the fuel tank along with a full tank of 95 or 98 octane fuel.

Petrol Injector Cleaner - 300mL | Supercheap Auto

Anyway, the links above are a very cheap way to try and DIY a solution before looing at the much more expensive solutions.