Not knowing you service records??
How long since a valve clearance check & compression check?
How old are the cap, rotor & wites?

Do you run premium fuel? 91+ octane?

Air flow position sensor is a COMMON failure that causes idle problems on 16V engines.

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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