Valve adjustment on a 16V isn't a diyER. Just having enough shims to make an adjustment will cost $150. Plus most people wouldn't have the expertize to remove & reinstall the cams to exchange these shims when needed.
Again MOST idle problems are related to AIR flow SENSOR problems.
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)