Recommend a compression check on all cylinders. I had a similar experience with a 1995 E320 … running fine, then suddenly started running rough while stopped at a traffic light. To make a long story short, turned out there was little/no compression in one cylinder. Not exactly sure what happened, but I was not about to spend big bucks repairing a vehicle that I bought for $4k, drove 100,000 miles, and had 200,000 miles on the odometer.

Good luck with the diagnosis. If your 1995 E420 is in pristine condition you may want to consider extensive/expensive repairs. That is a very personal decision … and can be very emotional.

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Fred Hoelzle