MB Kompressor engines have a PCV valve to control crankcase ventilation.

IF that valve sticks (& they do) then you will have oil in the intake area. That oil doesn't burn well & also causes damage to the Mass air flow sensor.

Have those systems checked for oil.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator