Possible top end failure - advice

[alexjfinch]

Good morning all,

I have a 2022 Polo 1.0L R-Line - which I believe has the 105 engine with engine code DLAC. The car is 4 years old with 20,800 miles on it, also auto.

Back in August, my partner was driving the car home and all of sudden it had loss of power and engine management light came on with an EPC light. I went to find her and it was misfiring. Call out recovery who put a code reader on it and found Cylinder 2 was misfiring. They recovered the vehicle back to my home and I went to GSF the next morning for a coilpack.

Changed the coilpack, which didn't work so I assumed it was DOA and went back for another. The second coilpack didn't work, so I did some crude diagnostics with swapping coils, spark plugs and unplugging the coilpacks and the misfire never seemed to moved from cylinder 2 and therefore diagnosed a faulty injector. At the same time I had a compression tester and tested all cylinders to equal pressure, so cylinder 2 had good compression.

The car was recovered to a specialist in Cardiff who went through everything and concluded the same and changed the injector for a brand new VW part. This didn't solve the issue. They then did more investigation and found that "sometimes" cylinder 2 would have low compression and using a borescope, found that one of the valves was sometimes sticking.

They explained they didn't have the tooling to strip the top end down and recovered the car back to my house, where its sat for weeks as we concluded it might be carbon build up and a carbon clean might work.

I've been thinking about it more and the car has a really loud tap when running (it also won't idle), which I think is a blocked or sticking lifter and therefore possibly causing the misfire. I've thrown in some lifter additive to see if it clears and it has become queiter but not cleared. My next idea is to probably strip the top end and inspect the valve assembly.

Couple of quick questions - feel free to throw me some ideas if you've come across something similar;

1.) I've found the workshop manual on the site, I understand the timing needs to be done with an electronic angle gauge. Is this required if I don't undo the cam sprockets? If I lock the cams with the toothed key and at the back of them, surely they don't move and I don't need to time it up with the angle gauge?
2.) Is there any other common areas I could be looking at for this - I doubt its carbon build up after 20k miles
3.) Any other things I need to be thinking about if I'm pulling the top end apart.

TIA!
Alex