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Inspection Procedure
8: Unstable Idling (Rough Idling, Hunting), Improper Idling Speed (too High or too Low), Engine
Stalls During Idling (Die Out)
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COMMENT ON TROUBLE SYMPTOM
- Probable causes can be widely found in ignition system, air-fuel ratio control
system, idle speed control system, fuel system, etc. A sudden engine stall is possibly caused
by poor connector contact.
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PROBABLE CAUSE
- Failed air-fuel ratio control system
- Failed idle speed control system
- Failed intake/exhaust system
- Failed emission gas cleaning system
- Throttle valve body fouled
- Compression pressure improper
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| STEP 1: Check battery condition. Q: Has the battery terminal been disconnected?
YES:
After warm-up engine, idle for about 10 minutes.
NO:
Go to Step 2  .
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| STEP 2: MUT-II/III diagnosis code Q: Diagnosis code set?
YES:
Inspection chart for diagnosis code (Refer to  ).
NO:
Go to Step 3 .
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| STEP 3: MUT-II/III data list - Refer to Data list reference table .
- Item 12: Air flow sensor
- Item 13: Intake air temperature sensor
- Item 14: Throttle position sensor
- Item 21: Engine coolant temperature sensor
- Item 25: Barometric pressure sensor
Q: Are the check results normal?
YES:
Go to Step 4 .
NO:
Perform the diagnosis code classified check procedure for the sensor that has
shown an abnormal data value (Refer to Inspection Chart for Diagnosis Codes ).
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| STEP 4: MUT-II/III data list - Refer to Data list reference table .
- Item 27: Power steering fluid pressure switch
Q: Are the check results normal?
YES:
Go to Step 5 .
NO:
Check power steering fluid pressure switch system (Refer to Inspection Procedure
29 ).
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| STEP 5: Check idle speed control servo for operating sound. - Check idle speed control servo for operating sound (Refer to ).
Q: Is the check result normal?
YES:
Go to Step 6 .
NO:
Check idle speed control servo system (Refer to Inspection Procedure 30 ).
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| STEP 6: Check throttle body (throttle valve portion) for contamination. Q: Is the check result normal?
YES:
Go to Step 7 .
NO:
Clean throttle body (throttle valve portion) (Refer to ).
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| STEP 7: Check air intake from intake hose and intake manifold. Q: Is the check result normal?
YES:
Go to Step 8 .
NO:
Repair.
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| STEP 8: Check injector for operating sound. - Check injector for operating sound (Refer to ).
Q: Can operating sound be heard?
YES:
Go to Step 9 .
NO:
- Check the injector system of the defective
cylinder
- (Refer to Code No. 41 ).
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| STEP 9: Check timing marks of timing belt. Q: Is the check result normal?
YES:
Go to Step 10 .
NO:
Align timing marks.
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| STEP 10. MUT-II/III data list - Refer to Data list reference table .
- Item 17: Mixture adjusting screw (variable resistor)
Q: Is the check result normal?
YES:
Go to Step 11 .
NO:
Check mixture adjusting screw (variable resistor) (Refer to Inspection Procedure
37 ).
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| STEP 11: Perform voltage measurement at C-111 engine-A/T-ECU. |
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- Measure engine-A/T-ECU terminal voltage.
- Voltage between terminal No. 66 and earth.
OK: System voltage
Q: Is the check result normal?
YES:
Go to Step 15 .
NO:
Go to Step 12 .
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| STEP 12: Connector check: C-111 engine-A/T-ECU connector |
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Q: Is the check result normal?
YES:
Go to Step 13 .
NO:
Repair.
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| STEP 13: Check harness between battery and C-111 (terminal No. 66)
engine-A/T-ECU connector |
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NOTE: Before checking harness, check the following intermediate connectors, and repair them
if necessary.
- A-14 <RHD>, C-02 <LHD>,
C-106, C-116 <LHD>, C-125 <RHD>, C-202 and C-204
- Check power supply line for open or short circuit or damage.
Q: Is the check result normal?
YES:
Go to Step 14
NO:
Repair.
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| STEP 14: Check the trouble symptoms. Q: Does trouble symptom persist?
YES:
Replace engine-A/T-ECU.
NO:
Intermittent malfunction (Refer to GROUP 00 -
How to Use Troubleshooting/Inspection
Service Points ).
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| STEP 15: Perform voltage measurement at C-111 engine-A/T-ECU connector. |
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- Measure engine-A/T-ECU terminal voltage.
- Voltage between terminal No. 42 and earth, also between terminal No. 48 and earth.
OK: 0.5 V or less
Q: Is the check result normal?
YES:
Go to Step 17 .
NO:
Go to Step 16 .
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| STEP 16: Connector check: C-111 engine-A/T-ECU connector |
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Q: Is the check result normal?
YES:
- Check and repair harness between C-111 (terminal
No. 42) engine-A/T-ECU connector and body earth.
- Check earthing line for open circuit and damage.
NO:
Repair.
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| STEP 17. Perform voltage measurement at C-112 engine-A/T-ECU connector. |
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- Measure engine-A/T-ECU terminal voltage.
- Engine: Idling after warm-up
- Selector lever position: P
- Radiator fan: Not operating
- Voltage between terminal No. 8 and earth.
OK: Switching the headlamps to ON from OFF causes the voltage to increase by 0.2 -
3.5 V.
Q: Is the check result normal?
YES:
Go to Step 20 .
NO:
Go to Step 18 .
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| STEP 18. Connector check: C-112 engine-A/T-ECU connector and B-30
alternator connector |
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Q: Is the check result normal?
YES:
Go to Step 19 .
NO:
Repair.
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| STEP 19. Check harness between C-112 (terminal No. 8) engine-A/T-ECU
connector and B-30 (terminal No. 1) alternator connector. |
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NOTE: Before checking harness, check intermediate connector B-19, and repair if necessary.
- Check output line for open/short circuit and damage.
Q: Is the check result normal?
YES:
Go to Step 20 .
NO:
Repair.
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| STEP 20. Perform voltage measurement at C-111 engine-A/T-ECU connector. |
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- Measure engine-A/T-ECU terminal voltage.
- Engine: Idling after warm-up
- Selector lever position: P
- Radiator fan: Not operating
- Voltage between terminal No. 54 and earth.
OK: Switching the headlamps to ON from OFF causes the voltage to fall.
Q: Is the check result normal?
YES:
Go to Step 24 .
NO:
Go to Step 21 .
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| STEP 21. Connector check: C-111 engine-A/T-ECU connector and B-30
alternator connector |
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Q: Is the check result normal?
YES:
Go to Step 22 .
NO:
Repair.
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| STEP 22. Check harness between C-111 (terminal No. 54) engine-A/T-ECU
connector and B-30 (terminal No. 4) alternator connector |
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NOTE: Before checking harness. check intermediate connector B-19, and repair if necessary.
- Check output line for open/short circuit and damage.
Q: Is the check result normal?
YES:
Go to Step 23 .
NO:
Repair.
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| STEP 23. Check the trouble symptoms. Q: Does trouble symptom persist?
YES:
Replace alternator.
NO:
Intermittent malfunction (Refer to GROUP 00 -
How to Use Troubleshooting/Inspection
Service Points ).
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| STEP 24. Perform voltage measurement at C-111 engine-A/T-ECU connector. |
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- Measure engine-A/T-ECU terminal voltage.
- A/C switch: ON (A/C compressor ON)
- Voltage between terminal No. 61 and earth.
OK:
- 1 V or less (with outside air temperature sensor ambient temperature at 18°C or
higher and A/C set for maximum air flow at minimum temperature)
- System voltage (with A/C set for minimum air flow at room temperature)
Q: Is the check result normal?
YES:
Go to Step 25 .
NO:
Check A/C load signal system (Refer to Inspection Procedure 26 ).
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| STEP 25. Connector check: B-110 and B-111 ignition coil connectors |
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Q: Is the check result normal?
YES:
Go to Step 26 .
NO:
Repair.
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| STEP 26. Check ignition coil spark. Q: Is the check result normal?
YES:
Go to Step 31 .
NO:
Go to Step 27 .
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| STEP 27. Check spark plug. Q: Is the check result normal?
YES:
Go to Step 28 .
NO:
Replace spark plug.
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| STEP 28. Check spark plug cable. - Check spark plug cable itself (Refer to GROUP 16 -
Ignition System -
On-vehicle
Service ).
Q: Q: Is the check result normal?
YES:
Go to Step 29 .
NO:
Replace spark plug cable.
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| STEP 29. Check ignition coil itself. - Check ignition coil itself (Refer to GROUP 16 -
Ignition System -
On-vehicle
Service ).
Q: Is the check result normal?
YES:
Go to Step 30 .
NO:
Replace ignition coil.
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| STEP 30. Check harness between terminal No. 2 of ignition coil connector
of each cylinder and body earth. |
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- Check earthing line for open/short circuit and damage.
Q: Is the check result normal?
YES:
- Check and repair harness between terminal
No. 3 of ignition coil connector of each cylinder and C-112 engine-A/T-ECU.
- Check signal line for open/short circuit and damage.
NO:
Repair.
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| STEP 31. Check injector for spray condition. - Check each injector for spray condition (Refer to ).
Q: Is the check result normal?
YES:
Go to Step 32 .
NO:
Replace injector.
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| STEP 32. Check compression pressure. - Check compression pressure (Refer to GROUP 11A -
On-vehicle Service ).
Q: Is the check result normal?
YES:
Go to Step 33 .
NO:
Repair.
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| STEP 33. Check EGR control solenoid valve itself. - Check EGR control solenoid valve itself [Refer to GROUP 17 -
Emission
Control System -
Exhaust Gas Recirculation (EGR) System ].
Q: Is the check result normal?
YES:
Go to Step 34 .
NO:
Replace EGR control solenoid valve.
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| STEP 34. Check EGR valve itself. - Check EGR valve itself [Refer to GROUP 17 -
Emission Control
System -
Exhaust Gas Recirculation (EGR) System ].
Q: Is the check result normal?
YES:
Go to Step 35 .
NO:
Replace EGR valve.
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| STEP 35. MUT-II/III actuator test OK: Operating sounds of fuel pump can be heard.
Q: Is the check result normal?
YES:
Go to Step 36 .
NO:
Check fuel pump system (Refer to inspection Procedure 24 ).
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| STEP 36. Replace engine-A/T-ECU - After engine-A/T-ECU is replaced, re-check for trouble symptoms.
Q: Does trouble system persist?
YES:
Check for foreign matters (water, kerosene, etc.) in fuel and replace if necessary.
NO:
Check end.
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