The Throttle Body Injection system used by the 4-cylinder Fiero uses an electric fuel pump. The throttle body is placed on the intake manifold where the carburetor is normally mounted. The TBI unit is computer controlled and supplies the correct amount of fuel during all engine operating conditions.
The unit is made primarily of aluminum and consist of two major casting assemblies, a throttle body and fuel metering assembly.
With the TBI system, air is drawn into a single bore. The fuel is then injected into the air stream under pressure. The unit contains a pressure regulator Idle Air Control (IAC) valve, and an electrically operated solenoid that activates the fuel injector. Also attached to the TBI is a Throttle Position Sensor (TPS), a fuel inlet and a fuel return fitting.