Where is the thermostat located on a 1985 Pontiac fiero gt?

The thermostat on a 1985 Pontiac Fiero GT is located in the engine block, at the rear of the engine. It's not readily accessible; you'll need to remove some components to get to it. Expect to work around the intake manifold and possibly other parts of the cooling system. A repair manual specific to that year and model Fiero will be very helpful for this job.