Had 3 unnerving surprises the past 2 days, when I give it maybe half or more throttle from a standing start, as in jumping out at a right-on-red. I let off the pedal and it keeps going - have to nail the brakes, at which time it does go back to normal. New symptom, ETA was replaced 3 years and 25k ago. Ideas?

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former: 83 300D, 97 C230, 93 400E

current: 08 C300 Luxury , 92 500SL