The O2 sensor sounds like one of the 'usual suspects'. I won't be able to crawl under my car for several weekends, but plan to do so. To that end, I did a search on this site for 'oxygen sensor'. This led to MANY hits. It seems that some of folks here have used an O2 sensor from a ford mustang - though some refer to it as a 302 mustang and some a 5.0 mustang, and the years vary a whole bunch. Does anyone have any experience with implanting a mustang sensor (ie part numbers or model and year, and which mercedes engines) into an E model mercedes?