Mitsubishi MOTORS Space Runner 1998, Руководство по ремонту

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GDI <4G9> -
General Information
13B-2
GENERAL INFORMATION
The Gasoline Direct Injection System consists
of sensors which detect the engine conditions,
the engine-ECU which controls the system
based on signals from these sensors, and
actuators which operate under the control of
the engine-ECU. The engine-ECU carries out
activities such as fuel injection control, idle
speed control and ignition timing control. In
addition, the engine-ECU is equipped with
several diagnosis modes which simplify
troubleshooting when a problem develops.
FUEL INJECTION CONTROL
The injector drive times and injector timing are
controlled so that the optimum air/fuel mixture
is supplied to the engine to correspond to the
continually-changing engine operation condi-
tions.
A single injector for each cylinder is mounted
at the cylinder head. The fuel is sent under
pressure from the fuel tank to the fuel pressure
regulator (low pressure) by the fuel pump (low
pressure). The pressure is regulated by the
fuel pressure regulator (low pressure) and the
fuel regulated is then sent to the fuel pump
(high pressure). The fuel under increased
pressure generated by the fuel pump (high
pressure) is then regulated by the fuel pressure
regulator (high pressure) and is then distributed
to each of the injectors via the delivery pipes.
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.
When the engine is cold or under a severe
load, the “open-loop” control keeps the air/fuel
ratio at a richer than usual level to maintain
driveability. When the engine is under low or
medium loads, the air/fuel ratio becomes leaner
to reduce fuel consumption. When the engine
is running at medium or high loads after having
warmed up, the “closed-loop” control uses the
signal from the oxygen sensor to keep the
air/fuel ratio at the optimum theoretical level.
IDLE AIR CONTROL
The idle speed is kept at the optimum speed
by controlling the amount of air that bypasses
the throttle valve in accordance with changes
in idling conditions and engine load during
idling. The engine-ECU drives the idle speed
control (ISC) motor to keep the engine running
at the pre-set idle target speed in accordance
with the engine coolant temperature and air
conditioner load. In addition, when the air
conditioner switch is turned off and on while
the engine is idling, the ISC motor operates
to adjust the throttle valve bypass air amount
in accordance with the engine load conditions
in order 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 current 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, atmospheric pressure and
injection timing (intake stroke or compression
stroke).
SELF-DIAGNOSIS FUNCTION
D 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.
D When an abnormality is detected in one
of the sensors or actuators, a diagnosis
code corresponding to the abnormality is
output.
D The RAM data inside the engine-ECU that
is related to the sensors and actuators can
be read by means of the MUT-
II
. In addition,
the actuators can be force-driven under
certain circumstances.