2010 Audi A5 2.0T - misfire, leak - smoke test - 5646 - Leak in Air Intake P2279

[vtraudt]

2010 Audi A4 2.0T quattro automatic (not sure what the engine code is for that car).

Car is idling terrible, tons of misfires.
Also oil leak rear of engine/transmission (bell housing)
Erased code, and 5646 P2279 comes back quickly.
Spark plugs black and build up (not worn much; not sure how hold).
Installed new plugs, no change.

Visually inspected hoses, nothing obvious.
Pancake small vent hole on PCV not showing bad behavior (had newer cars that were blowing/sucking out of that hose, indicating ripped bladder inside).
Oil cap come off normal with engine running (had cases where bad PCV created tremendous amount of suction, impossible to remove oil cap)

Rented 'smoker'. Removed air intake box and MAF, and smoked car through large intake hose.

Found smoke blowing out of PCV housing
Found smoke (some) coming out of top of timing belt cover front of engine
Found TONS of smoke coming out of bell housing bottom of engine

New PCV coming today.

Never had smoke coming out of the bell housing on any of the cars (1.8T, 2.7T). Is that normal for the 2.0T that smoke (massive) gets from intake hose right into bell housing?
If not, what might allow that to happen? Bad check valve somewhere?

I plant to swap in another set of ignition coils I have on hand, but the misfires at idle do NOT seem to be ignition related, rather air leak related (runs better at higher rpm).

Other suggestions for troubleshooting bad misfires at idle?

[van462]

Likely your your rear main seal has failed. It is allowing air into the engine and thru the PCV into your intake to where it reads a lean condition. Also why you have smoke and oil leak there.

[kt883]

Requires drop of transmission to correct the seal which is likely a cheap part itself. Quoted 11hr job

[vtraudt]

Likely your your rear main seal has failed. It is allowing air into the engine and thru the PCV into your intake to where it reads a lean condition. Also why you have smoke and oil leak there.

Figured. Oil leak = air leak.

Replace rear main seal, issues resolved.