The TBI system is used on all 1989-95 2.5L engines, 1989-91 3.9L and 5.2L engines and 1989-92 5.9L engines. There are two systems: single point and dual point. As you might expect, single point uses only one fuel injector and dual point uses two injectors. The 2.5L uses single point, while the V6 and V8 engines use dual point injection. Although there are some component differences between models, both single point and dual point systems share basic operation and service procedures.
Both systems are controlled by a pre-programmed digital computer known as a Single Module Engine Controller (SMEC) on 1989 models, Single Board Engine Controller (SBEC) on 1990-91 models, Engine Controller on 1992 models, and Powertrain Control Module (PCM) on 1993-95 models. The computer controls ignition timing, air/fuel ratio, emission control devices, charging system and idle speed. The computer constantly varies timing, fuel delivery and idle speed to meet changing engine operating conditions.