Mitsubishi Eclipse. Manual - part 637

 

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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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