You may also wanna check your spark plugs or change them and the wires altogether. I'm no mechanic, but I have a 190E ('90) 245,xxx miles on it and I had a rough idle and I didnt know what it was, so I read a few threads and then changed out the spark plugs and wires which solved the problem. I then had my O2 sensor changed bec the last time I had it replaced was when I had my spark plugs changed around 12/06. Car is running great now.