A rough running motor or lack of power can be caused by a failed distributor cap or rotor, ignition wires (or their resistors), or valve cover gasket leaks. If the valve cover gasket leaks, oil can pool where the ignition wire resistor connects to the spark plug. The resistor can fail and the spark plug may not fire because of a short circuit through the oil.Google+
Car Problem Reports
Mercedes-Benz 300E Engine Problems Due to Distributor Cap and Rotor, Bad Ignition Wires, or Valve Cover Gasket Leaks
Mercedes-Benz 300E Problem
Average Mileage: 125,300 mi (115,600 mi - 135,000 mi)
Visitor, 1990 Mercedes-Benz 300E
2 Water pump hoses replaced and the engine runs rough now. I don't think the tensioner belt was replaced.
Visitor, 1993 Mercedes-Benz 300E, 115,600 mi
Engine misfired, mechanic said a tune up is needed. Just wondering whats the cost for the tune up?
Carbon connection for the coil wire appeared o.k. but had no electrical continuity. Replacement of cap fixed problem.