GM Firebird 1982-1992 Repair Guide

System Description

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The throttle body injection (TBI) system used on 2.5L (VIN 2) and 5.0L (VIN E) engines is centrally located on the intake manifold. Its function is to supply the correct air/fuel mixture to the engine, as directed by the Engine Control Module (ECM).

The TBI unit consists of two relatively simple casting assemblies: a throttle body and a fuel metering assembly. Components include, a pressure regulator, idle air control valve, fuel injector(s), throttle position sensor, fuel inlet and a fuel return fitting.

The Throttle Body Injection identification number is stamped on the lower mounting flange located near the TPS. The number is in alphabetical code and should be noted before servicing the unit.

An oxygen sensor in the exhaust system functions to provide feedback information to the ECM as to oxygen content in the exhaust. The ECM then uses this information to modify fuel delivery to achieve as near as possible an ideal air/fuel ratio of 14.7:1. This ratio permits the catalytic converter to become more effective in reducing emissions while providing acceptable driveability.

Should you encounter any type of engine performance problem, have a complete CCC system test performed by a qualified, professional technician. If the fault lies in the injection system, you can use the following procedures to remove the TBI unit and replace the defective component(s).

 
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