EEC-IV Theory/Operation: Description

The heart of the EEC-IV system is the Electronic Control Assembly (ECA). The ECA receives information from various sensors and switches. Based on information received and the operational program in the ECA's memory, the ECA generates output signals to control engine operation. In addition to controlling engine function, the ECA also controls gear shift and Lock-Up Solenoid (LUS) functions for the AXOD automatic transmission and Torque Converter Clutch Override (CCO) function on vehicles equipped with the A4LD automatic transmission. The calibration module for EEC-IV system is mounted inside the ECA. See ECA LOCATION table for location of ECA module.

The EEC-IV system controls 3 major areas of engine operation: air/fuel mixture, ignition timing, and emission control. Additionally, the system can control A/C compressor clutch operation and idle speed. The system provides self-diagnostic capabilities.

The EEC-IV ignition system is controlled by the ECA through a Thick Film Integrated (TFI-IV) ignition module. Ignition timing (advance or retard) and dwell are controlled with this system to improve ignition system performance.

Air/fuel mixture operation is accomplished by one of 3 different fuel injection systems depending on engine size and vehicle model. A Multi-Point Fuel Injection (MPFI) system, Central Fuel Injection (CFI) system or Sequential Electronic Fuel Injection (SEFI) system may be used. See FUEL INJECTION SYSTEM APPLICATIONS  table.

Emission control components controlled by this system include EGR and canister purge. These systems are normally off, but are turned on when a mixture change signal allows operation of these units.