An engine wash resulted in my father's '93 E320 coupe requiring a new engine wiring harness. The harness was crumbling anyway but the moisture was sufficient to finish it off. I can't say I have heard of the harness in the C220 of any of the other 4-cylinder models giving the same trouble. Yours is in the right era ('92 - '95) for it to be a possibility since just about any other model from this era suffered from faulty wiring insulation (and you mentioned that the harness had been noted as failing). First ensure that everything else is dry around the spark plugs and ignition coils (2 coils on your M111 engine and no it does not have a distributor).

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107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.