1991 MITSUBISHI 3000GT engine coolant

FUEL SYSTEM - Service Adjustment Procedures13-33THROTTLE BODY
(THROTrLE VALVE AREA)
CLEANINGM13FICS
(1) Start the engine, warm it up until engine coolant tempera-ture rises to
80°C (176”F), and stop the engine.
(2) Disconnect the air intake hose at the throttle body side.
(3) Put a plug in the inlet of bypass passage in the throttle
body.
CautionNever allow cleaning agent to flow into the bypass
passage.(4) Spray cleaning agent from the intake port of the throttle
body to the valve and leave as it is for 5 minutes or so.
(5) Start the engine and race it several times. Then, run it idlefor approx. one minute.
NOTE
If the engine idle speed becomes unstable (and fails in theworst case) after plugging the bypass passage, run the
engine with the throttle valve slightly opened.
(6) If the deposit cannot be removed from the throttle valve,
repeat steps (4) and (5).
(7) Disconnect the plug from the inlet of the bypass passage.(8) Install the air ‘intake hose.
(9) Use a multi-use tester to erase the self-diagnosis code ordisconnect the battery ground cable for more than
IOseconds and then connect it again.
(lO)Adjust the basic idle speed (speed adjusting screw). (Referto
P.13-31.)
7FUO629
ADJUSTMENT OF IDLE POSITION SWITCH AND
THROTTLE POSITION SENSOR (TPS)M13FIFA(1) Disconnect the throttle position sensor connector.
(2) Using jumper wires, connect an ohmmeter across terminal
@ (idle position switch) and terminal @ (sensor ground) ofthe throttle position sensor.
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13-36FUEL SYSTEM - 0
n-vehicle Inspection of MPI Components
ON-VEHICLE INSPECTION OF MPI COMPONENTS
COMPONENTS LOCATION
EGR control solenoid valve
temperature sensor
Engine control unit
Engine coolant temperature sensor
Engine warning light
Fuel pressure control valve
Ignition coil (power transistor)
Ignition timing adjusting terminal
SSelf-diagnosis output terminal and self-diagnosis/Rdata transmission selector terminal
BTDC sensor and crank angle sensorD
PThrottle position sensor (with built-in idle switch)C
vVariable induction control servo (DC motor)J(with built-in induction control valve position
sensor)
MVehicle speed sensor (reed switch)F
QWaste gate solenoid valve U
NOTEThe “Name” column is in alphabetical order.TSB Revision

FUEL SYSTEM - On-vehicle Inspection of MPI Components13-55
INSPECTIONUsing Multi-use Tester

Function
Data readingtern No. Data display
12Sensor airvolume(frequency)
Check conditionEngine stateStandard value
l Engine coolant tem-
700 rpm (Idle)25-50 Hzperature: 80 to 95°C
(176 to 205°F)2,000 rpm70-IOOHzl Lights and accessories:OFFRacingFrequency increasesl Transaxle: Neutralwith racing(P range for vehiclewith AIT)l Steering wheel: Neutral
NOTEWhen the vehicle is new [within initial operation of about 500 km (300 miles)], the air flow sensor output frequency maybe about 10% higher.

Function
Data listItem No. Data displayCheck conditionsEngine conditionsStandard value
34Reset signall Engine warm up700 rpm (Idle)ON
condition2,000 rpmOFF
L;
FunctionItem No. Data display
Data list37Volumetric
efficiencyCheck conditionEngine stateStandard valuel Engine coolant tem-700 rpm (Idle)20-35%
perature: 80 to 95°C
(176 to 205°F)
l Lights, electric cooling2,000 rpm15-30%
fan and accessory opera-tion: OFFl Transaxle: NeutralRacingFrequency increases
(P range for vehiclewith racingwith &T)
l Steering wheel: Neutral
Using Oscilloscope(1) Run the engine at idle speed.
(2) Connect the probe to the oscilloscope pick-up point as
shown in the circuit diagram, and check the waveform.
Regular waveform
03A0203
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13-62FUEL SYSTEM- On-vehicle Inspection of MPI Components
ENGINE COOLANT TEMPERATURE SENSORM13Ybu2
1
If
il\__ ;I\*
Coolant temperature
162458Coolant temperaturei67im-m
Coolant temperature sensor
@ Equipment side
connector
2
fi
I
Engine control unit ), 72A63
1 ff35V
7FUO667
OPERATION
lThe engine coolant temperature sensor converts the engine coolant temperature into a voltage and inputsit to the engine control unit, which then controls the fuel injection rate and fast idle speed when the
engine is cold based on the input signal.
l The 5 V power in the engine control unit is supplied via a resistor in the unit to the engine coolant
temperature sensor. Through the sensor which is a kind of resistor, it is grounded in the engine control
unit. The engine coolant temperature sensor resistor has such characteristic that its resistance decreasesas the coolant temperature rises.
lThe engine coolant temperature sensor terminal voltage increases or decreases as the sensor resistance
increases or decreases. Therefore, the engine coolant temperature sensor terminal voltage changes withthe coolant temperature, decreasing as the temperature rises.
TROUBLESHOOTING HINTS
If the fast idle speed is inadequate or the engine emits dark smoke during engine warm up operation, theengine coolant temperature sensor is often faulty.
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id
LFUEL SYSTEM
- On-vehicle Inspection of MPI Components13-63
INSPECTIONUsing Multi-use Tester
LFunctionItem No. Data displayCheck condition
Coolant temperatureStandard valueData reading 21
SensorIgnition switch: ON or
At -20°C (-4°F)-20°C
temperatureengine operatingAt 0°C (32°F)0°C
HARNESS INSPECTION
Check for continuity of the groundcircuit.l Connector: Disconnected
Repair the---+ harness.

7FUO6682
Measure the power supply voltage.l Connector: Disconnected
@ Harness sidel Ignition switch: ON
7FUO669TSB Revision

13-64FUEL SYSTEM - 0
n-vehicle Inspection of MPI Components
7FUO670
Apply sealant
7FUO67’SENSOR INSPECTION
(1) Remove engine coolant temperature sensor from the
intake manifold.(2) With temperature sensing portion of engine coolant
temperature sensor immersed in hot water, check resis-
tance.
Temperature
“C (“F)Resistance (kCI)
0 (32)5.8
20 (68)2.4
40 (104)1.1
80 (176)0.3
(3) If the resistance deviates from the standard value greatly,
replace the sensor.
INSTALLATION
(1) Apply sealant to threaded portion.
Specified sealant: 3M NUT locking Part No. 4171 or
equivalent
(2) Install engine coolant temperature sensor and tighten it to
specified torque..Sensor tightening torque: 30 Nm (22
ft.lbs.)
(3) Fasten harness connectors securely.TSB Revision

13-72FUEL SYSTEM - On-vehicle Inspection of MPI Components
CRANK ANGLE SENSOR
co.ntiector
Output characteristic
LTime
7FUO682
MllYiAC
Control relay-I-
Crank angle sensorsideA3
Crank angle sensor/\
‘=
Engine controlunft69I
1
h5v
7FUO499
OPERATIONl
The crank angle sensor senses the crank angle (piston position) of each cylinder, converts it into a pulse
signal and inputs it to the engine control unit, which then computes the engine speed and controls the fuelinjection timing and ignition timing based on the input signal.
lPower to the crank angle sensor is supplied from the control relay and is grounded to the body. The crank
angle sensor generates a pulse signal as it repeatedly connects and disconnects between 5 V voltagesupplied from the engine control unit and ground.
TROUBLESHOOTING HINTSHint 1: If unexpected shocks are felt during driving or the engine stalls suddenly during idling, shake the
crank angle sensor harness. If this causes the engine to stall, poor contact of the sensor connector is
suspected.Hint 2: If the crank angle sensor outputs a pulse signal when the ignition switch is turned ON (with the
engine not running), a faulty crank angle sensor or engine control unit is suspected.
Hint 3:
If the tachometer reads 0 rpm when the engine that has failed to start is cranked, faulty crank angleHint 4:sensor or broken timing belt is suspected.
If the tachometer reads 0 rpm when the engine that has failed to start is cranked, the primary current
of the ignition coil is not turned on and off. Therefore, troubles in the ignition circuit and ignition coil orfaulty power transistor is suspected.
Hint 5: If the engine can be run at idle even though the crank angle sensor reading is out of specification,troubles are often in other than the crank angle sensor.
[Examples](1) Faulty engine coolant temperature sensor
(2) Faulty idle speed control servo
(3) Poorly adjusted reference idle speed
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FUEL SYSTEM - On-vehicle Inspection of MPI Components13-73
INSPECTION
Using Multi-use Tester
FunctionItem No. Data displayCheck conditionCheck content
Normal stateData reading 22
Crankingl Engine cranking
Compare cranking speedIndicated speed
speedl Tachometer connectedand multi-use tester(check on and off ofto agree
reading
primary current of
ignition coil bytachometer)
NOTE(1)The tachometer indicates a third of the actual engine speed. Therefore, 3 times the tachometer indication is theactual engine speed.(2)When the tachometer is set to the 2-cylinder range, it indicates actual engine speed.
FunctionItem No. Data displayCheck conditionCoolant temperatureStandard value
Data reading22Idle speedl Engine: Running atAt -20°C (-4°F)1,300 - 1,500 rpm
idle
l Idle position switch:ONAt 0°C (32°F)At 20°C (68°F)
At 40°C (104°F)
At 80°C (176°F)1,250
- 1,450 rpm
1
,I 00 - 1,300 rpm
950-1,150rpm
600 - 800 rpm
-m-2,-5v
f-lov
---Normal waveform
Using Oscilloscope
(1) Run the engine at idle speed.
(2) Connect the probe to the oscilloscope pick-up point as
shown in the circuit diagram, and check the waveform.
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