[LaiPSniS_]

Hey everyone,

I’m hoping someone here might have some insights or advice. I recently bought a 2011 BMW E92 328xi with the N51 SULEV engine and an automatic transmission. The car had a rough idle when I got it and occasionally stalled if I was driving slowly. After a week, I decided to take it to a mechanic to get it sorted out.

What’s been done so far:

Initial repairs:
Changed all spark plugs and one ignition coil.
Replaced the valve cover gasket due to an oil leak.
Cleaned the vanos solenoids and their filters.

However, after these fixes, the car still ran roughly and was giving misfire codes on cylinders 4, 5, and 6, along with a MAF sensor error.

Second round of repairs:
Mechanic kept the car for 3 weeks and diagnosed a faulty MAF sensor and a problem with the valve cover itself (they said it had a large gap).
Replaced the MAF sensor and the valve cover.
Cleaned the filters again, reinstalled the ECU, and reset all adaptations.

Current situation:
The car runs a lot better than before—it doesn’t stall when driving at low speeds anymore. However, when I’m stopped at a red light or when the car is in park, the RPMs fluctuate slightly, and there’s a small shake that I can still feel. It’s subtle, but definitely noticeable.

Other details that might be relevant:
Previous owner swapped the engine, but it’s still an N51 as it was originally.
The car burns oil. Before the repairs, it was using about 0.5 liters per 1,000 km. However, after driving about 500 km since the repairs, the oil level (according to the electronic dipstick) hasn’t dropped yet, so maybe that’s improved?
The mechanics suggested it could be either the piston rings or the valve stem seals that are causing the oil consumption. Could this be related to the rough idle?
Whenever the idle gets rough, I notice there’s more smoke from the exhaust. When the RPMs stabilize, there’s still some smoke but not as much.
Catalytic converter has been deleted, in case that’s relevant.
I’ve attached some OBD2 scanner readings (though I’ve read that INPA gives better results, which I don’t have access to).
My questions:
Has anyone dealt with a similar issue? Should I be looking for a mechanic who specializes in electrical diagnostics or one who’s more focused on mechanical work?
Could the valve stem seals or piston rings be contributing to the rough idle, especially since the car burns oil?
Any thoughts on whether the MAF sensor replacement and adaptation reset may not have fully solved the problem? Should I be checking other sensors or components?

I appreciate any advice or experiences you can share. I’m really enjoying the car when it’s running smoothly, but this rough idle issue is driving me nuts! Thanks in advance!