I predict the problem will return in a few months! (I had an M103 once upon a time. )

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

Not likely so long as it is not burning a lot of oil.....Bosch plugs would have been ideal over Champions though.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

With respect, sir, "Don't be depressing!"

If the plugs were that bad, replacement may be the cure. But if they had been badly neglected, what about the cap/rotor etc.

So, I stick by what I said. Make sure the ignition system is 100%.

Also, make sure that all electrical connections are clean. I have a policy of pulling connectors, spraying with good quality switch cleaner, plug/unplug to friction-clean the contacts and then refit with maybe a last spray to dissipate deposits. Do this to every connector you can find. It costs little and can be theraputic.

I have a very smooth idle that experts have commented on and this is at 350 K Kms and 18 years old, never garaged - it lives outside in all weathers.

Start with the cheap-to-replace items but don't buy cheap after-market. Ideally, get branded MB parts. Cap, rotor, HT leads may be a priority for you given that the plugs appear to have been neglected.

Bon courage.

RayH