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You need to start with a basic tune up and replace the coolant temp sensor. Chances are this will resolve all your issues. The computer is disabling the cruise due to the misfire code.
The misfire may be coming and going depending on conditions like air temp and engine temp. The temp sensor error may be there all the time and just not triggering a check engine light. The tune up is the first step and will most likey fix it. But it needs to be done to rule out weak plugs as the cause.
The sensor is less tha $30