a 15 year old car that needs maintenance is a lemon? Regarding the misfires, take a close look at the connectors going into the coils - they can crack and arc similar to bad wires. Regarding the overheating at random - does the car boil over or do you just have a wandering temperature gauge? If you have a wandering gauge, and haven't done so already, replace the thermostat and the engine coolant temp sensor (its just below the thermostat housing - you need to pop off the t-stat cover so its a good time to do both). Also replace the overflow tank cap.