Why would it lose power after its warmed up ?

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This car starts easily, idles smooth, runs, drives, after it warms up the oil light and the check engine light comes on and a sudden loss of power ,acceleration after a stop to get any speed is very difficult ? This happens every time I try to drive it .. Year: 1993 Make: Mercury Model: Sable Trim: LS Premium Body: Sedan Mileage: 99,325 Transmission: Automanual Liters: 3.8L Cylinders: 6 Thank You for you help and input..