Mitsubishi Lancer Evolution IX. Manual — part 479
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-391
Wave Pattern Observation Points
Point A: Height of solenoid back electromotive force
Point B: Injector drive time
•
The injector drive time will be synchronized with the
M.U.T.-II/III tester display.
• When the engine is suddenly raced, the drive
time will be greatly extended at first, but the drive
time will soon match the engine speed.
IDLE SPEED CONTROL (ISC) SERVO
(STEPPER MOTOR)
Measurement Method
1. Disconnect the idle speed control servo
connector, and connect the special tool test
harness (MB991709) in between.
2. Connect the oscilloscope special patterns pickup
to the idle speed control servoside connector
terminal No. 1, No. 3, No. 4 and No. 6
respectively.
Alternate Method (Test harness not
available)
1. Connect the oscilloscope special patterns pickup
to engine-ECU terminal No. 14, connection
terminal No. 28, connection terminal No. 15, and
connection terminal No. 29 respectively.
Standard Wave Pattern
Observation conditions
Contrast with standard
wave pattern
Probable cause
Solenoid coil back
electromotive force is
low or doesn't appear at
all.
Short in the injector
solenoid
AKX01605AE
When idling
When racing
1 2 3
5
4
6
AK201856AB
Special
patterns
pickup
Oscilloscope
Function
Special patterns
Pattern height
High
Pattern selector
Display
Engine condition
When the engine coolant
temperature is 20
°C or
below, turn the ignition
switch from "LOCK"
(OFF) position to ON
(without starting the
engine).
While the engine is
idling, turn the A/C
switch to ON.
Immediately after
starting the warm
engine.
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-392
Wave pattern Observation Points
Check that the standard wave pattern appears when
the stepper motor is operating.
Point A: Presence or absence of induced electromo-
tive force from the motor turning (Refer to the abnor-
mal wave pattern).
Point B: Height of coil reverse electromotive force
Examples of Abnormal Wave Pattern
•
Example 1
Cause of problem
Motor is malfunctioning. (Motor is not operating.)
Wave pattern characteristics
Induced electromotive force from the motor turn-
ing does not appear.
•
Example 2
Cause of problem
Open circuit in the line between the stepper
motor and the engine-ECU.
Wave pattern characteristics
Current is not supplied to the motor coil on the
open circuit side (Voltage does not drop to 0
V).
Furthermore, the induced electromotive force
waveform at the normal side is slightly differ-
ent from the normal waveform.
AK201857
30
20
10
(V)
Stepper
motor
control
signal
wave
pattern
The wave pattern
appears for an
instant, but soon
disappears.
Point B
Coilreverse electromotive
force (Approx.3x10V)
Standard wave pattern
Point A
Induced electromotive force
from the motor turning
Time
AB
Contrast with standard wave
pattern
Probable
cause
Induced electromotive force does
not appear or is extremely small.
Motor is
malfunctioning
Contrast with standard wave
pattern
Probable
cause
Coil reverse electromotive force
does not appear or is extremely
small.
Short in the
coil
AKX01608AE
AKX01609AF
Open
circuit
side
Normal
side
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-393
IGNITION COIL AND POWER TRANSIS-
TOR
Measurement Method
1. Disconnect the ignition coil connector, and
connect the special tool test harness (MB991348)
in between (All terminals should be connected).
2. Connect the oscilloscope special patterns pickup
to terminal No. 3 of each ignition coil connector in
turn.
Alternate Method (Test harness not
available)
1. Connect the oscilloscope special patterns pickup
to engine-ECU terminal No. 11 (No. 1
− No. 4),
connection terminal No. 12 (No. 2
− No.3)
respectively.
Standard Wave Pattern
Observation condition
AK201750
1 2 3
CH1
AB
Special
patterns
pickup
Oscilloscope
Function
Special patterns
Pattern height
Low
Pattern selector
Display
Engine r/min
Approximately 1,200
r/min
AK204435
2
2
0
0
4
4
6
(V)
Crank angle
sensor output
wave pattern
Power transistor
control signal
wave pattern
75˚ BTDC
5˚ BTDC
T
Compression top dead center
T1
T1 : Time computed by the engine-ECU
T : Revolution time corresponding to a crank angle of 180˚
Ignition period
OFF
ON
Dwell section
: Spark advance angle
AC
Standard wave pattern
TROUBLESHOOTING
MULTIPORT FUEL INJECTION (MPI)
13A-394
Wave Pattern Observation Points
Point: Condition of wave pattern build-up section and
maximum voltage (Refer to abnormal wave pattern
examples 1 and 2).
Examples of Abnormal Wave Patterns
•
Example 1
Wave pattern during engine cranking
Cause of problem
Open-circuit in ignition primary circuit
Wave pattern characteristics
Top-right part of the build-up section cannot be
seen, and voltage value is approximately 2 V
too low.
•
Example 2
Wave pattern during engine cranking
Cause of problem
Malfunction in power transistor
Wave pattern characteristics
Power voltage results when the power transistor
is ON.
Condition of wave pattern
build-up section and maximum
voltage
Probable cause
Rises from approximately 2 V
to approximately 4.5 V at the
top-right
Normal
2 V rectangular wave
Open-circuit in
ignition primary
circuit
Rectangular wave at power
voltage
Power transistor
malfunction
AKX01612AD
Normal wave pattern
2V
AKX01613AD
Normal wave pattern
V
B
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