Powertrain Management: Description and Operation

PGM-FI System Description:

PURPOSE
The 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
MPFI Control
The PGM-FI 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.
Idle Air Control
When the engine is cold, the A/C is on, or the alternator is charging, the PGM-FI ECM controls current to the Idle Air Control (IAC) Valve to maintain correct idle speed.
Ignition Timing Control
The PGM-FI 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 PGM-FI system monitors and controls the functions of the Exhaust Gas Recirculation (EGR) System. By reading the signal sent by the EGR lift sensor the PGM-FI ECM can determine, then control the vacuum supplied to operate the EGR Valve. The PGM-FI ECM also controls when the Evaporative Emission (EVAP) Control Canister is purged of fuel vapors by controlling the vacuum applied based on input from sensors on the engine.
Fuel Supply System
The PGM-FI system controls the power supplied to the fuel pump to supply fuel to the system as required.