If you had foamy coolant that can point to a serious problem, or at the very least it could be minor.
I would suggest you properly pressure test the system, which can be done with a tool that can be rented from places that rent tools. If you have an Autozone near you, they rent a coolant system pressure tester. You will want to test both the ability for the radiator cap to hold pressure, and pressure test the actual cooling system itself. At the very least, your radiator cap may have lost the ability to properly pressurize the system, which usually results in coolant loss or other issues.
On the other side of this, foamy coolant can suggest head gasket or some other more serious failure. In addition to head gasket failure causing the system to improperly pressurize, it can let things in like exhaust and intake mixtures into the coolant, thus causing it to foam.
If you're unsure about these situations on a Fiero, my suggestion is you check out The Orge's Cave (it's at the top of EVERY forum page here on PFF) and look up his methods for proper cooling system diagnosis and problem solutions.
[This message has been edited by Fiero84Freak (edited 07-16-2013).]