Car: 97 C230, 145K miles

Problem: a couple of weeks ago my C230 suddenly experienced a CEL, ran rough.. no power..

I borrowed a OBD-II meter > the CEL code read that #4 was misfireing. I subsequently replaced all spark plugs [they had better than 80K on them] and seemingly all was fine .

A few days later > car experienced another CEL, code read #4 misfire . I replaced the spark plug boot and thought all was fine

Car ran great for a few more days .. then yesterday > same thing.. car > when cold runs great for about 30 min.. then it MIGHT suddenly misfire > #4 misfire and it chugs along on 3 cylinders.

Why does it do that?? I've replaced the spark plug and the spark plug cap..

Is it the coil?

recommendation for fix??

__________________
Kim Langley
97 C-230
80 911 SC
73 2002Tii