Page 652 of 1449
MPI -Troubleshooting13A-120
Standard wave pattern
(V)
Point A
Point BSolenoid back electromotive force
(Approx. 7×10 V)
Injector drive time
Power voltage
Drive signal: ON Drive signal: OFF
Time 50
0
Wave Pattern Observation Points
Point A: Height of solenoid back electromotive force
Contrast with standard wave patternProbable cause
Solenoid coil back electromotive force is low or doesn’t
appear at all.Short in the injector solenoid
Point B: Injector drive time
DThe injector drive time will be synchronized with the MUT-II
tester display.
DWhen the engine is suddenly raced, the drive time will
be greatly extended at first, but the drive time will soon
match the engine speed.
When idling
When racing ---
--
Page 653 of 1449

MPI -Troubleshooting13A-121
IDLE SPEED CONTROL 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 analyzer special patterns pickup to the idle
speed control servo-side connector terminal No. 1,
terminal No. 3, terminal No. 4 and terminal No. 6
respectively.
Alternate Method (Test harness not available)
1. Connect the analyzer special patterns pickup to
engine-ECU terminal No. 4, connection terminal No. 5,
connection terminal No. 17, and connection terminal No.
18 respectively.
Standard Wave Pattern
Observation conditions
FunctionSpecial patterns
Pattern heightHigh
Pattern selectorDisplay
Engine conditionWhen the engine coolant temperature is 20_C or below, turn the ignition switch from “LOCK”
(OFF) position to “ON” position (without starting the engine).
While the engine is idling, turn the A/C switch to ON.
Immediately after starting the warm engine
Standard wave pattern
Stepper
motor
control
signal
wave
pattern(V)
30
20
10The wave pattern
appears for an
instant, but soon
disappears.Point B
Coil reverse electromotive
force (Approx. 3×10 V)Point A
Induced electromotive force
from the motor turning
Time
Special
patterns
pickupAnalyzer
Page 654 of 1449

MPI -Troubleshooting13A-122
Wave Pattern Observation Points
Check that the standard wave pattern appears when the stepper motor is operating.
Point A: Presence or absence of induced electromotive force from the motor turning. (Refer to the abnormal
wave pattern.)
Contrast with standard wave patternProbable cause
Induced electromotive force does not appear or is extremely small.Motor is malfunctioning
Point B: Height of coil reverse electromotive force
Contrast with standard wave patternProbable cause
Coil reverse electromotive force does not appear or is extremely small.Short in the coil
Examples of Abnormal Wave Pattern
DExample 1
Cause of problem
Motor is malfunctioning. (Motor is not operating.)
Wave pattern characteristics
Induced electromotive force from the motor turning does
not appear.
DExample 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 different from the normal
waveform.
Open
circuit
side
Normal
side
Page 655 of 1449

MPI -Troubleshooting13A-123
IGNITION COIL AND POWER TRANSISTOR
DIgnition coil primary signal
Refer to GROUP 16 - Ignition system.
DPower transistor control signal
Measurement Method
1. Disconnect the ignition coil connector, and connect the
special tool (test harness: MB991658) in between. (All
terminals should be connected.)
2. Connect the analyzer special patterns pickup to terminal
No. 3 of each ignition coil connector in turn.
Alternate Method (Test harness not available)
1. Connect the analyzer special patterns pickup to
engine-ECU terminal No. 10 (No. 1 - No. 4), terminal
No. 23 (No. 2 - No. 3) respectively.
Standard Wave Pattern
Observation condition
FunctionSpecial patterns
Pattern heightLow
Pattern selectorDisplay
Engine r/minApproximately 1,200 r/min
Standard wave pattern
Crank angle
sensor output
wave pattern
Power transistor
control signal
wave pattern(V)
75_BTDC5_BTDCT: Revolution time corresponding to a crank angle of 180_
Compression top dead center
θ: Spark
advance
angleIgnition period
OFF ON
Dwell section
T1: Time computed by the engine-ECUTime θ T1T
6
4
2
0
4
2
0
Special
patterns
pickupAnalyzer
Page 662 of 1449

MPI -On-vehicle Service13A-130
14. If any of fuel pressure measured in steps 10 to 13 is out of
specification, troubleshoot and repair according to the
table below.
SymptomProbable causeRemedy
DFuel pressure too low
DFuelpressuredropsafterracing
Clogged fuel filterReplace fuel filter
DFuelpressuredrops after racing
DNo fuel pressure in fuel return
hose
Fuel leaking to return side due to poor
fuel regulator valve seating or settled
springReplace fuel pressure regulator
Low fuel pump delivery pressureReplace fuel pump
Fuel pressure too highBinding valve in fuel pressure
regulatorReplace fuel pressure regulator
Clogged fuel return hose or pipeClean or replace hose or pipe
Same fuel pressure when vacuum
hose is connected and when
disconnected
Damaged vacuum hose or clogged
nippleReplace vacuum hose or clean nipple
disconnectedFuel pressure control system
malfunctionCheck the fuel pressure control
system
15. Stop the engine and check change of fuel pressure gauge
reading. Normal if the reading does not drop within 2
minutes. If it does, observe the rate of drop and
troubleshoot and repair according to the table below.
SymptomProbable causeRemedy
Fuel pressure drops gradually after
engineisstopped
Leaky injectorReplace injector
engineisstopped
Leaky fuel regulator valve seatReplace fuel pressure regulator
Fuel pressure drops sharply
immediately after engine is stoppedCheck valve in fuel pump is held openReplace fuel pump
16. Release residual pressure from the fuel pipe line.
(Refer to P.13A-125.)
17. Remove the fuel pressure gauge and special tool from
the delivery pipe.
Caution
Cover the hose connection with rags to prevent splash
of fuel that could be caused by some residual pressure
in the fuel pipe line.
18. Replace the O-ring at the end of the fuel high pressure
hose with a new one. Furthermore, apply engine oil to
the new O-ring before replacement.
19. Fit the fuel high pressure hose over the delivery pipe
and tighten the bolt to specified torque.
Tightening torque: 5.0±1.0 N·m
20. Check for any fuel leaks by following the procedure in
step 7.
21. Disconnect the MUT-II.
Page 663 of 1449
MPI -On-vehicle Service13A-131
COMPONENT LOCATION
NameSymbolNameSymbol
A/C relayJFuel pump relay 1, 2Q
A/C switchTFuel pump relay 3H
Air flow sensor (integrated intake air tempera-
ture sensor and barometric pressure sensor)OFuel pump resistorH
Camshaft position sensorNIdle speed control servo (stepper motor)G
Crank angle sensorKIgnition coil (integrated power transister)M
Detonation sensorEInjectorC
Diagnosis connectorSOxygen sensor (front)L
EGR control solenoid valveDOxygen sensor (rear)X
Engine control relayIPower steering fluid pressure switchA
Engine coolant temperature sensorNResistor (for injector)H
Engine warning lamp (check engine lamp)RSecondary air control solenoid valveD
Engine-ECUUThrottle position sensorG
Fan motor relayJVehicle speed sensorF
Fuel pressure control solenoid valveBWaste gate solenoid valveP
ABCDEFGHIJK
LMNOP
QRSTU
Page 673 of 1449
MPI -Injector13A-141
INJECTOR
REMOVAL AND INSTALLATION
Pre-removal and Post-installation Operation
DFuel Discharge Prevention (Refer to P.13A-125.)
DStrut Tower Bar Removal and Installation
(Refer to GROUP 42.)DAir Hose E, Air By-pass Hose, Air Pipe C Removal
and Installation (Refer to GROUP 15 - Intercooler.)
DFuel Leakage Check
21
3
13 5
6
7
8 9 1011 12
4
8.9±1.9N·m
8.9±1.9N·m 5.0±1.0N·m
Apply engine oil to all
moving parts during
installation.
14 15
16 12
6
5.0±1.0N·m
Removal steps
1. Control harness connector
2. Accelerator cable assembly
connection (Throttle body side)
3. Injector harness connector
"AA4. High-pressure fuel hose connection
5. O-ring
6. Fuel return hose connection
7. Vacuum sensor connector
"AA8. Fuel pressure regulator9. O-ring
10. Fuel return pipe
AA"11. Delivery pipe
12. Insulator
13. Insulator
AA""AA14. Injector
15. Grommet
16. O-ring
Page 674 of 1449

MPI -Injector13A-142
REMOVAL SERVICE POINT
AA"DELIVERY PIPE/INJECTOR REMOVAL
Remove the delivery pipe (with the injectors attached to it).
Caution
Care must be taken, when removing the delivery pipe,
not to drop the injector.
INSTALLATION SERVICE POINT
"AAINJECTOR/FUEL PRESSURE REGULATOR
/HIGH-PRESSURE FUEL HOSE INSTALLATION
1. Apply a drop of new engine oil to the O-ring.
Caution
Be sure not to let engine oil enter the delivery pipe.
2. While turning the injector, high-pressure fuel hose and
fuel pressure regulator to the right and left, install the
delivery pipe, while being careful not to damage the O-ring.
After installing, check that the hose turns smoothly.
3. If it does not turn smoothly, the O-ring may be trapped,
remove the injector, high-pressure fuel hose or fuel
pressure regulator and then re-insert it into the delivery
pipe and check once again.
4. Tighten the high-pressure fuel hose and fuel pressure
regulator to the specified torque.
Tightening torque:
5.0±1.0 N·m (High-pressure fuel hose)
8.9±1.9 N·m (Fuel pressure regulator)