I second Will's suggestion.

I just went through "bogging" with my '95 E420. Sporadic bogging - usually after the car running OK for a few minutes, if shut off, upon restart the bogging would appear almost mysteriously.

Suspecting water in the gas or clogged fuel filter (which I had had once about 3 years ago)....I replaced the fuel filter. No improvement.

So, I drained the fuel tank (just aft of the fuel pump), and put in a full tank of fresh, high octane (Sunoco), and threw in a bottle of octane boost for the heck of it.

Voila, problem cured. Remains cured for about 3 full tanks now.

So, while not the solution to all M119 engine problems, definitely a solution one should try as it does not require lots of work or replacement of expensive parts.

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Syntax26

1995 MB E420 (lowered)
1989 MB 300SE (sold to brother)
1975 MB 280 (sold)
One damn fine jacked-up golf cart