Mercury Mystique

Hy guys! I have a Mercury Mystique 96, 4 cyl. 2.0, automatic, with 157000 miles (I replaced the engine when it had 70000); but the transmission is the original one. I drive a lot (+/- 150 m/day) and I try to keep the car in great shape, maintenancewise. Today, it lost power, started to sputter, and check engine light began to flash like crazy, and the car just wouldn't go faster than 30 mph. Never stalled though. I removed one of the spark plugs, and one was soaked in oil. It did not overheat and I could hear the radiator fan work at times. No leaks, no smoke, just the typical heavy hesitation noise. So what kind of problem do I have now? Anything really serious? Thanks ahead of time.
June 18, 2007.

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