1991 MITSUBISHI 3000GT check engine

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

FUEL SYSTEM - On-vehicle Inspection of MPI Components13-65
i
1
THROTTLE POSITION SENSORM13YJAC
Maximum
Throttle shaft
turning angle
162481
Minlmum
@ Unleaded
Equipment side
connectorThrottle positron sensor
I
@ Harness side
connector
Ii
SEL14001
Engine control unit ,
I
Engine control unit connector
7FUO672
7FUO653
OPERATIONl
The throttle position sensor converts the throttle position opening into a voltage and inputs it to the enginecontrol unit, which then controls the fuel injection based on the input signal.
l
The 5 V power in the engine control unit is supplied to the throttle position sensor. Through the resistor inthe sensor, it is grounded in the engine control unit.
l
As the throttle valve shaft rotates from the idle position to Wide open position, the resistance between the
variable resistor terminal of the throttle position sensor and the ground terminal increases. As a result, thevoltage at the throttle position sensor variable resistance terminal also increases.
TROUBLESHOOTING HINTS
Hint 1: The throttle position sensor signal is more important in the control of automatic transaxle than in theengine control. Shifting shock and other troubles will be caused if this sensor is faulty.
Hint 2: If the output voltage of the throttle position sensor is out of specification, adjust the sensor and
check the voltage again. If there is an evidence of disturbed idle position switch (fixed SAS) setting,adjust the idle position switch (fixed SAS).
1 TSB Revision

13-66FUEL SYSTEM - 0n-vehicle Inspection of MPI Components
INSPECTIONUsing Multi-use Tester
FunctionItem No. Data displayCheck conditionThrottle valveStandard value‘d
Data reading14SensorIgnition switch: left ONvoltagefor 15 seconds or moreAt idle position300-1.000 mV
Open slowly
Increases withvalve opening
Open widely4.500-5.500 mV
HARNESS INSPECTIONl Connector: Disconnected
l
lgnrtion switch: ON
l Connector: Disconnected
connector
I
Engine controlCheck for an open-circuit, or a short-
unit harnesscircuit to ground between the engine
side connectorcontrol unit and the throttle positionsensor.
Throttle position sensor connec-
tor: Disconnected
Engine control unit connector:
DisconnectedRepair theB-3 harness.
km-8)
-z =6FU1243
[ TSB Revision

13-68FUEL SYSTEM - On-vehicle Inspection of MPI Components
IDLE POSITION SWITCHMlBYKAD
Throttle positionse(Idle position switch
2
/bz----;-p
b+i
Throttle shaft turning angle D’20g2
i
Engine control unitI
@ Harness side
connectorIdle position,
@ Equipment side switchconnector
Throttle position
sensor connector
5EL1400
7FUO674
OPERATIONl The idle position switch senses whether the accelerator pedal is depressed or not, converts it into
high/low voltage and inputs the voltage to the engine control unit, which then controls the idle speed
control servo based on the input signal.
lThe voltage in the engine control unit is applied to the idle position switch through a resistor. When the
accelerator pedal is released, the idle position switch is turned on to conduct the voltage to ground. Thiscauses the idle position switch terminal voltage to go low from high.
TROUBLESHOOTING HINTS
If the idle position switch harness and individual part check results are normal but the idle position switchoutput is abnormal, the following troubles are suspected.
’(1) Poorly adjusted accelerator cable or auto-cruise control cable
(2) Poorly adjusted idle position switch (fixed SAS)
INSPECTIONUsing Multi-use Tester
FunctionItem No. Data displayCheck conditionThrottle valveNormal indicationData reading 26
Switch state
Ignition switch: ONON(check by operatingAt idle position
accelerator pedalOpen a littleOFF-J
repeatedly)TSB Revision

iFUEL SYSTEM
- On-vehicle Inspection of MPI Components
INSPECTION
Using Oscilloscope13-71
::Normal waveform(1) Run the engine at an idle speed.
(2) Connect the probe to the oscilloscope pick-up point as
shown in the circuit diagram, and check the waveform.
7Fuo495HARNESS INSPECTION
= 7FUO496r
i2
@ Harness sideconnectorF
7FUO497
J
Measure the power supply voltagel Connector: Disconnected
l Ignition switch: ON
Voltage
(VI, OK(I:
sv
ib
02
Repair the
harness.
(@m - Con-
trol relay)
ICheck for continuity of the groundcircuit.l Connector: Disconnected
3
~,
Check the voltage of the output err-cuit.l Connector: Disconnected
l Ignition switch: ON
Voltaae
(V)4.8
- 5.2Repair the
harness.
(@El-ED
I7FUO498
idliTSB Revision

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.
1 TSB Revision

FUEL SYSTEM - On-vehicle Inspection of MPI Components
L
L
IGNITION SWITCH-ST
lgnitlon switch (ST)
I
Enaine control unit connector
7FUO653
Engine control unit
1 FU0638
OPERATION
lThe ignition switch-ST inputs a high signal to the engine control unit while the engine is cranking. Theengine control unit provides fuel injection control, etc., at engine startup based on this signal.
lWhen the ignition switch is set to START, the battery voltage at cranking is applied through the ignitionswitch to the engine control unit, which detects that the engine is cranking.
INSPECTION
Using Multi-use Tester
FunctionItem No. Data displayCheck conditionEngineNormal indication
Data reading18Switch stateIgnition switch: ONstopOFF
CrankingON
HARNESS INSPECTION
1
L6FU1258
2
1
Engine control
side connector
IY-6FU1259
Measure the input voltage to theengine control unit.nlEngine control unit connector:Disconnectedl Ignition switch: START
Check for continuity of the groundcircuit.
lEngine control unit connector:Disconnected
Repair the
harness.
(m - Ground)
iTSB Revision

13-76FUEL SYSTEM - On-vehicle Inspection of MPI Components
IGNITION SWITCH-ST AND INHIBITOR SWITCH
lqnition switch (ST)
@ Equipment side
connectorStarter S Control
terminalrelay
f,BL
Engine control unit connector7FUO625
Engine control unit
@ Harness side
connector
7FUO653
OPERATIONl
The ignition switch-ST inputs a high signal to the engine control unit while the engine is cranking. Theengine control unit provides fuel injection control, etc., at engine startup based on this signal.
l
When the ignition switch is set to START, the battery voltage at cranking is applied through the ignitionswitch and inhibitor switch to the engine control unit, which detects that the engine is cranking.
In case the selector lever is in a position other than the P/N range, the battery voltage is not applied to theengine control unit.
l
The inhibitor switch converts the selector lever position (whether it is at the P/N range or at others) into
high/low voltage and inputs it to the engine control unit, which then controls the idle speed control servobased on this signal.
l
The battery voltage in the engine control unit is applied through a resistor to the inhibitor switch. When the
selector lever is set to the P/N range, continuity is produced between the inhibitor switch terminal of the
engine control unit and ground through the starter motor, thereby making the terminal voltage go low.
TROUBLESHOOTING HINTS
If the inhibitor switch harness and individual part check have resulted normal but the inhibitor switch output isabnormal, poorly adjusted control cable is suspected.
TSB Revision