Restricted flow for any reason is same, engine runs hot or worse.
Temp Gauge on dash often lies, scan ECM for temp, check T-stat tube w/ IR or other temp meter, etc, before doing any work.
If coolant pipes under car is bent even a little you have Crushed Pipe
Remove/loosen support hardware to look at rear of pipes at minimum.
Many Fiero have broken rocker panels and body damage too because morons jack the car wrong.
Beyond that, most T-stant can make big temp swings more so at idle or low speeds.
Replace T-stant w/ Stant superstant. Even tho may look same as others, is not and stops wide temp swings.
See my Cave, Thermostat
and most of rest of section.
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
The Ogre's Fiero Cave