General System Description

PGM-FI System Description:

PURPOSE
The Programmed Fuel Injection (PGM-FI) System used on this vehicle is designed to monitor and control engine management functions and components including the air/fuel mixture, idle speed and ignition timing to achieve optimum engine performance.

OPERATION
The Engine Control Module (ECM) contains memories for the basic discharge durations at various engine speeds and manifold pressures. The basic discharge duration, after being read out from memory, is further modified by signals sent from various sensors to obtain the final discharge duration.
The ECM also functions also include control of several other subsystems.

Idle Air Control
The ECM controls current to the Idle Air Control (IAC) Valve to maintain correct idle speed.

Ignition Timing Control
The ECM contains memories for basic ignition timing at various speeds and manifold pressures. Ignition timing is also adjusted for engine coolant temperatures.

Emission Control Devices
The ECM monitors the signal sent by the Exhaust Gas Recirculation (EGR) lift sensor and controls the vacuum supplied to operate the EGR Valve. It also controls when the Evaporative Emission (EVAP) Control Canister is purged of fuel vapors by controlling the vacuum applied through the Purge Control Solenoid Valve.

Fuel Supply System
The PGM-FI system supplies the ground for the main relay, which, in turn, controls power to the fuel pump.