EEC IV Theory/Operation: Description
The center of the EEC-IV system is the Electronic Control Assembly (ECA). The ECA receives information from several sensors and other electronic devices. Based on information received and the operation program in the ECA's memory, the ECA generates output signals to control engine operation. The calibration module for EEC-IV systems is mounted inside the ECA. The ECA is located in the passenger compartment, under the center console.
The EEC-IV system controls 3 major areas of engine operation. These areas are, air/fuel mixture, ignition, and emission control. Additionally the system controls A/C compressor clutch operation and provides self-diagnostic capabilities.
The air/fuel mixture control is accomplished by an air flow controlled, multi-point, fuel injection system. Items controlled by the fuel injection system are the fuel injectors, deceleration fuel shut-off, curb idle and fast idle speed, fuel pump, cold engine enrichment.
The ignition system is controlled by the ECA through a Thick Film Ignition (TFI) module. Ignition timing (advance or retard) and dwell are controlled with this system to improve ignition system performance.
Emission control components controlled by this system include the EGR system and the canister purge system. These systems are shut off until the engine and controls are ready to operate with the changed conditions presented by EGR and canister purge operation.