3.0D (M57N) Tapping/Knocking/Ticking?

[zuvarak]

Hello everyone

I own a 2005 X5 with M57N (3.0D) EURO3 engine, which came without the DPF and swirl flaps from the factory.

I just had the exhaust manifold changed because it was cracked. The shop suggested changing the valve cover gasket as well with new injector washers.

Picked the car up, everything was well. On the same evening, I started the car and heard quite a loud continuous tapping noise from the engine bay. Tapping increased with more revs.

Started it up a few days later and it was running quite rough, the vibrations were felt inside as well. Connected it with INPA and injector values were quite horrible.



Now I don't know how exactly the injector balancing logic works, but I assumed that 4th was overflowing, and5th was brought down to compensate.
I took some correctional reading about a month ago and they were all within tolerances I suppose, the highest positive value was 1.75 (4th cyl).

After seeing the corrections, I figured that the tapping I heard was due to a faulty injector. I found a local shop to quickly try and diagnose the issue (last day of MOT is on 31.12, lucky me). They switched some injectors around and the corrections remained the same.

Once it was kind of clear that it's probably not injector-related, they proceeded to remove the intake, and here's the result:


Smoke is coming out of the 4th cylinder intake. Did the guys who did my exhaust manifold do something wrong while in there? Was something dropped into the intake? **** knows, maybe it's just a coincidence. I truly hope it's not a bent valve.. The shop also removed the valve cover and said that everything looks alright there, no broken rockers/springs.. and said that the next step would be removing the cylinder head in order to understand what's really wrong. The guy said that if there's some kind of build-up and the valves aren't closing/opening properly, it might be possible to clean them without removing the head. I figure that before stripping off the head, it would make sense to find a camera of sorts that would allow examining the valves from inside the cylinder.. I think I heard that something like this exists.