I purchased a used 2002 C230K Sport Coupe recently. After driving it for two weeks, the Service Engine light began glowing on startup. At the same time, I noticed that the engine would surge slightly, speeeding up and down in a rhythm when driving at a steady rate, either with or without the speed control engaged.

I installed new correct plugs and changed the air filter, but the problem persists. I also feel the gas mileage is lower than I would expect, getting a steady 25 mpg on my 100 mile roundtrip commute on highway (70 mph) and some open two-lanes (12 miles at 60 mph)

Is there a way to reset the Service Light without going to the dealer or a shop, such as disconnecting the battery for a time? How abut the mileage? Thanks for any asistance you folks can supply.

Richard