check engine MITSUBISHI 3000GT 1991 Manual Online

13-104FUEL SYSTEM - On-vehicle Inspection of MPI Components
-l4Harness side
connector
L----.[ Q1J
7FUO971
‘Y-4 ’onnector for
7FUO78C
Check for an open-circuit, or a short-circuit between the rear bank injectorand the engine control unit.l Connector: Disconnected
l
Engine control unit connector:
Disconnected
I
ACTUATOR INSPECTIONMeasurement of Resistance between Front Bank Termi-
nals(1) Remove the injector connector.
(2) Measure the resistance between terminals.
Standard value: 13
- 16 il [at 20°C (68”F)](3) Install the injector connector.
Measurement of Resistance between Rear Bank Terminals
(I) Remove the injector connector.
(2) Measure the resistance between terminals.
Standard value: 13
- 16 Q [at 20°C (68”F)](3) Install the injector connector.
\
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13-106FUEL SYSTEM - On-vehicle Inspection of MPI Components
INSPECTION
Using Multi-use Tester
FunctionItem No.Data displayCheck conditionCoolant temperatureStandard value‘L,,,J
DataDrive time*’0°C (32’F)*’readingiRea:bankiEngine: CrankingApprox. 53 ms
(FronT7bank)20°C (68°F)
Approx. 29 ms
80°C (176°F)Approx. 7 ms
FunctionItem No.
Data displayCheck conditionEngine stateStandard value
Datareading(Reaebank)Drive time*3l Engine coolant tem-700 rpm (Idle)1.9 - 2.5 ms
perature: 80 to 95°C
(Front7banki(176 to 205°F)2,000 rpm1.6 - 2.2 ms
l Lamps, electric coolingfan, accessory units:To increase
All OFFWhen sharp racing is
made
l Transaxle: Neutral(P range for vehicle
with A/T)
l Steering wheel: Neutral
NOTE“I : The injector drive time refers to when the supply voltage is 11 V and the cranking speed is less than 250 rpm.
“2: When coolant temperature is lower than 0°C (32°F). injection is made by four cylinders simultaneously.
“3: When the vehicle is new [within initial operation of about 500 km (300 miles)], the injector drive time may be about
10% longer.
Function
Actuator testItem No.
Drive contentCheck conditionNormal state
01No. 1 injector shut offEngine: Idling afterIdle state to changewarm-upfurther (becoming less
02No. 2 injector shut off(Shut off the injectorsstable or stalling)
03in sequence during afterNo. 3 injector shut offengine warm-up, checkthe idling condition)
04No. 4 injector shut off
05
No. 5 injector shut off
06
No. 6 injector shut off
\,iUsing
OscillqscopeI(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 at
the drive side of each injector.~
-
LJ
4 AL A: InjectorNormal waveformdrive time03A0209
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FUEL SYSTEM - On-vehicle Inspection of MPI Components13-107
HARNESS INSPECTION
@ Harness sideconnector
I
I
7FUO976
Measure the power supply voltage of
the resistor.
l Resistor connector: Discon-
nectedl Ignition switch: ON
connector
7FUO669-I
3Rear bank
harness side
connector
.------------------’7FUO97;
Harness sideconnectorz7FUO805
Measure the power supply voltage of
the front bank injector.
l Resistor connector: Connected0 Injector connector: Disconnected
l Ignition switch: ON
Voltage
(V)
0
OK03
Repair the
harness.
(@g@pJ-Control relay)Check power
supplyCheck resis-tor
Measure the power supply voltage ofthe rear bank injector.l Connector: Disconnected
l Ignition switch: ON
*
04
Repair the
supply’Check resis-tor
Check for an open-circuit, or a short-circuit between the front bank injector
and the engine control unit.
f---l -
l Injector connector: DisconnectedlEngine control unit connector:
Disconnected
1
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13-108
IFUEL SYSTEM
- 0n-vehicle Inspection of MPI Components
------+ Rear bankconnector 1
Check for an open-circuit, or a short-circuit between the rear bank injectorand the engine control unit.l Connector: Disconnected
l
Engine control unit connector:
Disconnected0
OKASTOP
Repair the
harness.
@ilT’ilpt-
iiWF4)
ACTUATOR INSPECTION
INJECTORSMeasurement of Resistance between Front Bank Termi-
nals
(1) Disconnect the injector connector.
(2) Measure the resistance between terminals.
Standard value: 2
- 3 R [at 20°C (68”F)](3) Reconnect the injector connector.
‘iJ
Measurement of Resistance between Rear Bank Terminals
(‘I ) Disconnect the injector connector.
(2) Measure the resistance between terminals.
Standard value: 2
- 3 R [at 20°C (68”F)](3) Reconnect the injector connector.
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13-110FUEL SYSTEM - On-vehicle Inspection of MPI Components
IDLE SPEED CONTROL SERVO (STEPPER MOTOR TYPE)\
7FUO64;Ball beam
‘9
L PlntleControl relay
@ Harness side
connector
\/1, \,\/“1“3 “4 “6Idle speed
control servo
OSCIIIOOSCIIIOOSClllOosclllomu--
/(a /(IT ),!j /I,, Enginecontrol unit
BPPP
7FUO518Engine control unit connector
7FUO653
OPERATION
lThe intake air volume during idling is controlled by opening ‘or closing the servo valve provided in the air
path that bypasses the throttle valve.’
lThe servo valve is opened or closed by operating the stepper motor in the speed control servo in normal or
reverse direction.
lThe battery power is supplied to the stepper motor through the control relay. As the engine control unit
turns on power transistors in the unit one after another, the stepper motor coil is energized and the motor
rotates in normal or reverse direction.
TROUBLESHOOTING HINTSHint 1:If the stepper motor step increases to 100 to 120 steps or decreases to 0 step, faulty stepper motor
or open circuit in the harness is suspected.
Hint 2: If the idle speed control servo harness and individual part checks have resulted normal but the
stepper motor steps are out of specification, the following faults are suspected.
(I) Poorly adjusted reference idle speed
(2) Deposit on the throttle valve
(3) Air leaking into the intake manifold through gasket gap
(4) Loose EGR valve seat
(5)Poor combustion in the cylinder (faulty ignition plug, ignition coil, injector, low compression
pressure, etc.)
\L.J
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FUEL SYSTEM - On-vehicle .lnspection of MPI Components13-111
INSPECTIONUsing Multi-use Tester
FunctionItem No. Data display
Data reading 45
Stepper
1
motor steps
~
Check condition
l Engine coolant tem-
perature: 80 to 95°C
(176 to 205°F)
0 Lamps, electric cooling
fan, accessory units:
All OFFl Transaxle: Neutral(P range for vehiclewith AA>l Steering wheel: Neutrall Idle position switch: ON(compressor clutch
to be ON if air condi-
tioner switch is ON)l Engine: idling
Load stateStandard value
;;rnditioner switch:2 - 12 stp&conditioner switch:
25 - 65 stp
l $irNconditioner switch:15 - 63 stp0 Selector lever:Shift to D range
NOTEWhen the vehicle is new [within initial operation of about 500 km (300 miles)], the stepper motor steps may be about 30steps more than standard.
CautionWhen the selector lever is shifted to the “D”range, the brakes must be used to prevent the vehicle frommovingforward.
03A020
Using Oscilloscope(1) Connect the probe to each oscilloscope pick-up point as
shown in the circuit diagram.
(2) Start the engine.
(3) When the air conditioner switch is turned on, the idling
speed increases to operate the idle speed control. Check
the instantaneous waveform.
NOTEKeep in mind that the waveform can be observed only
when idle speed control is in operation.
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13-112FUEL SYSTEM - 0
n-vehicleInspection of MPI Components
HARNESS INSPECTION
Measure the power supply voltage ofidle speed control servo.l
Idle speed control servo connec-tor: Disconnectedl Ignition switch: ON
Connector
connector
OlLO395- WI)
Engine control
Check for an open-circuit, or a short-circuit to ground between the enginecontrol unit and the idle speed control
servo.l
Engine control unit connector:
Disconnectedl
Idle speed control servo connec-tar: Disconnected
ACTUATOR I’NSPECTIONChecking the Operation Sound
(1)Check that the operation sound of the stepper motor can be
heard after the ignition is switched ON (but without starting
the motor).
(2) If the operation sound cannot be heard, check the stepper
motor’s activation circuit.
If the circuit is normal, it is probable that there is a
malfunction of the stepper motor or of the engine control
unit.
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13-116FUEL SYSTEM - 0
n-vehicle Inspection of MPI Components
INSPECTION
Using Multi-use Tester
(d
FunctionItem No. Data displayCheck condition
Engine state
Standard valueData reading 44
Ignitionadvancel Engine: Warming up
750 rpm (Idle)7 - 23”BTDCl Timing light: Set (settiming light to check2,000 rpm30 - 40”BTDC actual ignition timing)28 - 35”BTDC

‘
Function
Data listItem No.Data displayCheckTerminalStandard value
condition
condition
36Continuity present or
not present betweenl Engine:
IdlingIgnition timing ad-ON
ignition timing adjustmentjustment terminal isterminal and groundgrounded
Ignition timing ad-OFFjustment terminal is
disconnected from
ground
Function
Actuator testItem No.
DriveCheck conditionNormal condition
17Set to ignition timingl Engine: idling5”BTDCadjustment model Timing light: set\
($Gizi)
IJ
\LIOV _
ovep~,. ..~_~.~ fA t---.-
I
Normal waveform03AO207
(
j /’ II
IOV _I ’/
/ 1ovIJ
Normal waveform
Using Oscilloscope1. Primary signal of ignition coil
(I) Run the engine at an idle revolution speed.
(2) Connect the probe to oscilloscope pick-up point 1 as
shown in the circuit diagram, and check the primary
signal of the ignition coil.
2. Control signal of power transistor
Connect the probe to oscilloscope pick-up point
2 as shown
in the circuit diagram, and check the control signal of the
power transistor.
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FUEL SYSTEM - On-vehicle Inspection of MPI Components13-117
HARNESS INSPECTION
connectorl Connector: Disconnected
l Ignition switch: ON
Check for an open-circuit, or a short-
P
circuit to ground between the engine
control unit and the power transistor.l
Engine control unit connector:
Disconnectedl
Power transistor connector: Dis-connectedEngineRepair thecontrolunit-+ harness.harness(@@J-1101/)stdeconnector
T6FU1251
Check for an open-circuit, or a short-circuit to ground between the power
transistor and the ignition coil.l
Ignition coil connector: Discon-netted
l
Power transistor connector: Dis-
connected
Repair the
7FUO699
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FUEL SYSTEM - On-vehicle Inspection of MPI Components13-119PURGE CONTROL SOLENOID VALVE
Q Harness side
connector
I
Control relay
@ Equipment side
connector connector
unit
OlAO324
Engine control unit connector
7FUO653OPERATION
lThe purge control solenoid valve is an ON-OFF type one which controls introduction of purge air from the
canister into the intake air plenum.
lThe battery power is supplied to the purge control solenoid valve through the control relay. When the
engine control unit turns ON the power transistor in the unit, current flows to the coil, introducing purge
air.
INSPECTION
Using Multi-use Tester
Function
Actuator testItem No.Drive content
Check conditionNormal state
08Solenoid valve from OFFIgnition switch: ONOperating sound is heard
to ONwhen driven
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