Toyota Celica 1986-1993 Repair Guide

Description of System


The Electronic Fuel Injection (EFI) system precisely controls fuel injection to match engine requirements, reducing emissions and increasing drivability. The electric fuel pump supplies fuel to the fuel pressure regulator. The 4 fuel injectors are electric solenoid valves which open and close by signals from the Electronic Control Unit (ECU).

The EFI computer receives input from various sensors to determine engine operating condition. The sensors provide the input to the control unit, which determines the amount of fuel to be injected by its preset program. Some of these sensors are:

Air flow meter: measures the amount of intake air.
Distributor: engine rpm.
Throttle position sensor: amount of throttle opening.
Water temperature sensor: temperature of coolant or engine.
Air temperature sensor: temperature of intake air (ambient temperature).
Starting switch: signals that the starter is operating.
Exhaust gas oxygen sensor: used to measure the oxygen content of the exhaust gas.
Vacuum sensor: measures the amount of intake manifold pressure.