GENERAL DESCRIPTION
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <2.4L ENGINE>
13A-3
.
G EN ER A L DESC RIPTIO N
M1131000100154
The Multiport Fuel Injection System consists of
sensors, actuators and the engine control module
(ECM) <M/T> or powertrain control module (PCM)
<A/T>. The sensors detect the engine condition. The
module controls the system based on signals from
these sensors. The actuators work under the control
of the ECM <M/T> or PCM <A/T>. The ECM <M/T>
or PCM <A/T> carries out activities such as fuel
injection control, idle air control, and ignition timing
control. In addition, the ECM <M/T> or PCM <A/T>
has several diagnostic test modes which simplify
troubleshooting when a problem develops. In
addition, the ECM <M/T> or PCM <A/T> is equipped
with several diagnostic test modes which simplify
troubleshooting when a problem develops.
FUEL INJECTION CONTROL
The ECM <M/T> or PCM <A/T> controls injector
drive times and injector timing to supply the optimum
air/fuel mixture to the engine according to the
continually-changing engine operation conditions. A
single injector is mounted at the intake port of each
cylinder. The fuel pump supplies pressurized fuel
from the fuel tank to the fuel injectors. The fuel
pressure regulator controls the fuel pressure. Thus,
the regulated fuel is distributed to each injector. Fuel
is normally injected for each cylinder every two
rotations of the crankshaft. The firing order is 1-3-4-
2. Each cylinder has a dedicated fuel injector. This is
called "multiport." The ECM <M/T> or PCM <A/T>
provides a richer air/fuel mixture by carrying out
"open-loop" control when the engine is cold or
running under high load conditions. Thus, engine
performance is maintained. In addition, when the
engine is under normal operating temperature after
warming-up, the ECM <M/T> or PCM <A/T> controls
the air/fuel mixture according to the heated oxygen
sensor signal. This control is a "closed-loop" control.
The closed-loop control achieves the theoretical air/
fuel mixture ratio where the catalytic converter can
obtain the maximum cleaning performance.
IDLE AIR CONTROL
The engine control module controls the amount of air
that bypasses the throttle valve according to
changes in idling conditions and engine load during
idling. Thus, idle speed is kept at an optimum speed.
The ECM <M/T> or PCM <A/T> drives the idle air
control (IAC) motor according to engine coolant
temperature, A/C, and other electrical load. Thus,
idle speed is kept at an optimum speed. In addition,
when the air conditioning switch is turned off and on
while the engine is idling, the IAC motor adjusts the
throttle valve bypass air amount. Thus, idle speed is
maintained at constant speed regardless of various
engine load conditions.
IGNITION TIMING CONTROL
The ignition power transistor located in the ignition
primary circuit turns on and off to control primary
current flow to the ignition coil. This maintains
ignition timing at an optimum level regardless of
various engine operating conditions. The ECM <M/
T> or PCM <A/T> determines the ignition timing
according to engine speed, intake air volume, engine
coolant temperature, and atmospheric pressure.
DIAGNOSTIC TEST MODE
•
When a fault is detected in any of the sensors or
actuators related to emission control, the
SERVICE ENGINE SOON/MALFUNCTION
INDICATOR LAMP illuminates to warn the driver.
•
When a fault is detected in one of the sensors or
actuators, a diagnostic trouble code
corresponding to the fault is stored in the ECM
<M/T> or PCM <A/T>.
•
The RAM data inside the ECM <M/T> or PCM
<A/T> that is related to the sensors and actuators
can be read with the scan tool. In addition, the
actuators can be controlled by the scan tool
MUT-II (MB991502) under certain circumstances.
OTHER CONTROL FUNCTIONS
1. Fuel Pump Control Turns on the fuel pump relay
so that current is supplied to the fuel pump while
the engine is cranking or running.
2. A/C Compressor Clutch Relay Control Turns on
and off the air conditioning compressor clutch.
3. Evaporative Emission Purge Control (Refer to
GROUP 17, Emission Control System
−
Evaporative Emission Control System
−
General
Information
P.17-90
.)
4. EGR Control (Refer to GROUP 17, Emission
Control System
−
Exhaust Gas Recirculation
(EGR) System
−
General Information
P.17-96
.)