Snoopy572, when was the oxygen sensor last changed? Our 1991 300CE had similar symptoms, though not as severe. Replacing the oxygen sensor eliminated the hesitation. You should also check the condition of the distributor cap, rotor, ignition wires and the spark plugs. The fuel filter should be replaced every 60,000 miles. If you're not sure when the fuel filter was last replaced I'd have it done as preventive maintenance.

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Fred Hoelzle