Help! Why does my car goes dead when its temperature rised?

Without knowing what brand car you have, you have two temperature sensors. One goes to your temperature gauge and the other to your power module. When you first start your car your computer module goes into a default, meaning, that all inputs (temperature, vacuum, etc) are preset by the computer. When your engine reaches a certain temperature, it signals the computer to get off default and start monitoring all inputs. You might want to check out if this sensor is not malfunctioning. It should be easy to locate it as most are installed around the front of the engine block in the vicinity of the water pump thermostat housing.