Quite some years ago, got a bad batch of diesel from the local Texaco. Almost immediately the engine started to knock and ping like a gasser being fed 30 octane gas. Was not able to dilute it, as it had been a full fill. Fairly quickly dumped almost the whole tank and refilled elsewhere. After the overflow lines mixed up the rest of the bad fuel, the problem was pretty much gone. By the way this was on the '61 190D maroon Ponton.

In some ways your situation sounds like it could be a water issue, but that is just a guess.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150