Q: Fiero begins to overheat when at idle/ driving slow

This can be caused by a number of things such as low coolant levels, a faulty thermostat, or a failing coolant fan switch. As you may know the coolant fan switch helps to maintain the proper coolant temperature by turning on and off at specific temperature thresholds. When this switch is not working properly, this can cause the fans to come on intermittently, all the time or sometimes not at all. When this happens you will notice a temperature spike and drop occasionally as the fan comes on and off. This may be more noticeable when sitting at a stop or idling vs driving down the highway due to the fact that there is no air blowing past the radiator to cool it off as it does when driving down the highway. When your thermostat is not working properly or is stuck closed, this will not allow the coolant to properly circulate through the engine, which may cause the engine temperature to fluctuate erratically or in some cases just remain hot. I would suggest having an expert from Your Mechanic come to your home to diagnose your cooling system.