Mitsubishi Eclipse. Manual — part 637
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <3.0L>
13B-1091
Standard Wave Pattern
Wave Pattern Observation Points
Point A: Height of injector coil induced voltage.
Point B: Injector drive time
1. The injector drive time should be synchronized with the
scan tool tester display.
2. When the engine is suddenly revved, the drive time will be
greatly extended at first, but the drive time will soon return
to original length.
Observation conditions
Function
Special pattern
Pattern height
Variable
Variable knob
Adjust while viewing the
wave pattern
Pattern selector
Display
Engine r/min
Idle speed
CONTRAST WITH STANDARD
WAVE PATTERN
PROBABLE CAUSE
Injector coil induced voltage is
low or doesn't appear at all
Short in the injector
solenoid
AKX01604
(V)
50
0
DRIVE SIGNAL:"ON"
POINT B:
INJECTOR DRIVE
TIME
POINT A
DRIVE SIGNAL:"OFF"
POWER VOLTAGE
INJECTION COIL INDUCED
VOLTAGE (APPROXIMATELY 50-60 V)
AB
Standard wave pattern
AKX01605
WHEN IDLING
WHEN RACING
AB
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <3.0L>
13B-1092
IDLE AIR CONTROL MOTOR (STEPPER MOTOR)
Required Special Tool:
• MB991709: Test Harness
.
Measurement Method
1. Disconnect the idle air control motor connector, and connect
the test harness special tool (MB991709) in between. (All
terminals should be connected.)
2. Connect the oscilloscope probe to the idle air control motor
connector terminal 1, terminal 3, terminal 4 and terminal 6,
respectively.
.
Alternate method (Test harness not available)
1. Connect the oscilloscope probe to ECM <M/T> or PCM
<A/T> terminals 14, 15, 28 and 29.
Standard Wave Pattern
Wave Pattern Observation Points
1. Check that the standard wave pattern appears when the
idle air control motor is operating.
Point A:
Presence or absence of induced electromotive force from the
motor turning. (Refer to abnormal wave pattern.)
Observation conditions
Function
Special pattern
Pattern height
High
Pattern selector
Display
Engine condition
Turn the ignition switch from "OFF" to
"ON" (without starting the engine).
While the engine is idling, turn the A/C
switch to "ON."
Immediately after starting the warm the
engine (approximately one minute).
AK102983AB
1 2 3
4 5 6
IDLE AIR CONTROL
MOTOR CONNECTOR
OSCILLOSCOPE
MB991709
AKX01607 AB
(V)
30
20
10
0
IAC
MOTOR
CONTROL
SIGNAL
WAVE
PATTERN
THE WAVE PATTERN
APPEARS FOR AN
INSTANT, BUT SOON
DISAPPEARS.
POINT B COIL RE-
VERSE ELECTRO-
MOTIVE FORCE
(APPROXIMATELY
3 x10 V)
POINT AN INDUCED
ELECTROMOTIVE
FORCE FROM THE
MOTOR TURNING
TIME
Standard wave pattern
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <3.0L>
13B-1093
Point B:
Height of coil back electromotive force
.
Examples of Abnormal Wave Patterns
Example 1
• Cause of problem
Malfunction of motor. (Motor is not operating.)
• Wave pattern characteristics
Induced electromotive force from the motor turning does not
appear.
Example 2
• Cause of problem
Open circuit in the line between the idle air control motor
and the ECM <M/T> or PCM <A/T>.
• Wave pattern characteristics
Current is not supplied to the motor coil on the open circuit
side. (Voltage does not drop to 0 volt.) Furthermore, the
induced electromotive force wave pattern at the normal side
is slightly different from the normal wave pattern.
IGNITION COIL AND IGNITION POWER
TRANSISTOR
Required Special Tool:
• MB991348: Test Harness Set
.
CONTRAST WITH STANDARD
WAVE PATTERN
PROBABLE CAUSE
Induced electromotive force does
not appear or is extremely small
Malfunction of motor
CONTRAST WITH STANDARD
WAVE PATTERN
PROBABLE CAUSE
Coil reverse electromotive force does
not appear or is extremely small
Short in the coil
AKX01608 AB
AKX01609
OPEN
CIRCUIT
SIDE
NORMAL
SIDE
AB
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI) <3.0L>
13B-1094
Measurement Method
1. Disconnect the connector, and connect test harness special
tool, (MB991348), in between. (All terminals should be
connected.)
2. Connect the oscilloscope probe to ignition coil connector
terminal 3.
.
Alternate method (Test harness not available)
1. Connect the oscilloscope probe to ECM <M/T> or PCM
<A/T> terminal 11.
Standard Wave Pattern
Wave Pattern Observation Points
Point: Condition of wave pattern build-up section and maximum
voltage (Refer to abnormal wave pattern examples 1 and 2.
Observation conditions
Function
Special pattern
Pattern height
Low
Pattern selector
Display
Engine r/min
Approximately 1,200 r/min
AK102985AB
1 2 3 4 5 6 7
DISTRIBUTOR
CONNECTOR
OSCILLOSCOPE
MB991348
AK000069
CRANKSHAFT
POSITION
SENSOR OUTPUT
WAVE PATTERN
(REFERENCE)
IGNITION POWER
TRANSISTOR
CONTROL SIGNAL
WAVE PATTERN
POINT:
WAVE BUILD-UP
SECTION
Standard wave pattern
θ
θ : SPARK ADVANCE ANGLE
ON
DWELL SECTION
TIME
OFF
T
T : CRANKSHAFT ANGLE (120˚)
COMPRESSION
TOP DEAD CENTER
0
2
4
6
0
2
4
6
(V)
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