I suggest that you start with a basics..does that & all cylinders have correct compression.?

If so then swapping that coil & wires to a GOOD running cylinder would be a test of that part.

Even swapping spark plugs from that cylinder to another is a possibility..new parts can be defective.

Making sure that that cylinder doesn't have a vacuum leak..

Re-initialization of the crank sensor will rectify MANY running problems on the M112/113 engines on most 1998 & later cars.

A lean mixture can affect 1 cylinder ONLY if the that cylinder is already running lean or poorly..

__________________
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