Mitsubishi Colt Ralliart. Manual — part 669

The Multipoint Fuel Injection System consists of sen-
sors which detect the engine conditions, the
engine-ECU which controls the system based on sig-
nals from these sensors, and actuators which oper-
ate under the control of the engine-ECU. The

engine-ECU carries out activities such as fuel injec-
tion control, idle speed control and ignition timing
control. In addition, the engine-ECU is equipped with
several diagnosis modes which simplify trouble-
shooting when a problem develops.

FUEL INJECTION CONTROL

The injector drive times and injection timing are con-
trolled so that the optimum air/fuel mixture is sup-
plied to the engine to correspond to the
continually-changing engine operation conditions.
A single injector is mounted at the intake port of each
cylinder. Fuel is sent under pressure from the fuel
tank by the fuel pump, with the pressure being regu-
lated by the fuel pressure regulator. The fuel thus
regulated is distributed to each of the injectors.
Fuel injection is normally carried out once for each
cylinder for every two rotations of the crankshaft. The
firing order is 1-3-4-2. This is called sequential fuel
injection. The engine-ECU provides a richer air/fuel
mixture by carrying out "open-loop" control when the

engine is cold or operating under high load condi-
tions in order to maintain engine performance. In
addition, when the engine is warm or operating under
normal conditions, the engine-ECU controls the
air/fuel mixture by using the oxygen sensor signal to
carry out "closed-loop" control in order to obtain the
theoretical air/fuel mixture ratio that provides the
maximum cleaning performance from the three way
catalyst.

THROTTLE VALVE OPENING CONTROL

This system electrically controls the opening of the
throttle valve. The engine-ECU detects the amount
of travel of the accelerator pedal via the accelerator
pedal position sensor, and controls the actuation of
the throttle valve control servo, which is mounted on
the throttle body, in order to attain the target throttle
valve opening that has been predetermined in
accordance with driving conditions.

IDLE SPEED CONTROL

The idle speed is kept at the optimum speed by con-
trolling the amount of air that passes through the
throttle valve in accordance with changes in idling
conditions and engine load during idling.

The engine-ECU drives the throttle valve control
servo to keep the engine running at the pre-set idle
target speed in accordance with the engine coolant
temperature and A/C and other electrical load. In
addition, when the air conditioning switch is turned
off and on while the engine is idling, the throttle valve
control servo adjusts the throttle valve passes
through air amount according to the engine load con-
ditions to avoid fluctuations in the engine speed.

IGNITION TIMING CONTROL

The power transistor located in the ignition primary
circuit turns ON and OFF to control the primary cur-
rent flow to the ignition coil. This controls the ignition
timing in order to provide the optimum ignition timing
with respect to the engine operating conditions. The
ignition timing is determined by the engine-ECU from
the engine speed, intake air volume, engine coolant
temperature and atmospheric pressure.

Main

Index

Group

TOC

GENERAL INFORMATION

MULTIPORT FUEL INJECTION (MPI) <4G1>

13B-3

SELF-DIAGNOSIS FUNCTION

• When an abnormality is detected in one of the

sensors or actuators related to emission control,
the engine warning lamp (check engine lamp)
illuminates as a warning to the driver.

• When an abnormality is detected in one of the

sensors or actuators, a diagnosis code corre-
sponding to the abnormality is output.

• The RAM data inside the engine-ECU that is

related to the sensors and actuators can be read
by means of the M.U.T.-III. In addition, the actua-
tors can be force-driven under certain circum-
stances.

OTHER CONTROL FUNCTIONS

1. Fuel Pump Control

Turns the fuel pump relay ON so that current is sup-

plied to the fuel pump while the engine is crank-
ing or running.

2. A/C Relay Control

Turns the compressor clutch of the A/C ON and OFF.

3. Oil Control Valve Control

The engine-ECU carries out the duty control of the oil

control valve according to the operation condi-
tion. This varies the phase angle of the intake
camshaft to optimize the intake valve timing.

4. Fan Motor Control

The revolutions of the radiator fan and condenser fan

are controlled in response to the engine coolant
temperature and vehicle speed.

5. Alternator Output Current Control

Prevents alternator output current from increasing

suddenly and idle speed from dropping at times
such as when the headlamp are turned on.

6. Purge Control Solenoid Valve Control

(Refer to

P.17-13

, GROUP 17

− Engine And Emis-

sion Control

− Evaporative Emission Control Sys-

tem).

Main

Index

Group

TOC

GENERAL INFORMATION

MULTIPORT FUEL INJECTION (MPI) <4G1>

13B-4

GENERAL SPECIFICATIONS

Items

Specifications

Throttle body

Throttle bore mm

Throttle position sensor

Hall element type

Throttle valve control servo

DC motor type, having broshes

Engine-ECU

Identification No.

E6T45179

Sensors

Barometric pressure sensor

Semiconductor type

Intake air temperature sensor

Thermistor type

Engine coolant temperature sensor

Thermistor type

Oxygen sensor

Zirconia type

Accelerator pedal position sensor

Hall element type

Camshaft position sensor

Magneto resistance element type

Crank angle sensor

Magneto resistance element type

Detonation sensor

Piezoelectric type

Actuators

Engine control relay type

Contact switch type

Fuel pump relay type

Contact switch type

Injector type and number

Electromagnetic type, 4

Injector identification mark

HDB305E

Throttle actuator control motor relay

Contact switch type

Oil feeder control valve

Duty cycle type solenoid valve

Purge control solenoid valve

Duty cycle type solenoid valve

Fuel pressure solenoid valve

ON/OFF type solenoid valve

Waste gate solenoid valve

Duty cycle type solenoid valve

Fuel pressure
regulator

Regulator pressure kPa

294

Main

Index

Group

TOC

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Mitsubishi Colt Ralliart. Manual — part 669

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