300TE 4MATIC (124.290) L6-3.0L (103.985) (1991)
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Fouled plug (may be caused by):
^ Rich air/fuel mixture
^ Retarded ignition timing
^ Oil in combustion chamber
^ Incorrect spark plug gap
^ Plug heat range too low
^ Excessive idling/low speed running
^ Clogged air cleaner element
^ Deteriorated ignition coil, coil wire or ignition wires
2.
Replace the plug if the center electrode is rounded.