I am not familiar with your car so take my advice with a grain of salt, but it sounds like a throttle cable or linkage between the gas pedal and your engine probably broke. Are you familiar with that part of your vehicle, and would you be able to poke around for any anomalies?

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).