Inspection Procedure 7: Unstable Idling (Rough Idling, Hunting), Improper Idling Speed (Too High or too Low), Engine Stalls during Idling (Die Out)






COMMENTS ON TROUBLE SYMPTOM



  • Probable causes can be widely found in the ignition system, air-fuel ratio control system, throttle valve control system, and fuel system, etc. A sudden engine stall is possibly caused by poor contact in the connectors.

PROBABLE CAUSES



  • Failed ignition system
  • Failed fuel system
  • Failed air-fuel ratio control system
  • Failed intake and exhaust air system
  • Failed exhaust gas cleaning system <Except vehicles for Russia>
  • Contamination around the throttle valve
  • Timing belt in out of place
  • Improper compression pressure
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III diagnosis code

Q. Is diagnosis code set?
Inspection chart for diagnosis code (Refer to ).
Go to Step 2 .

STEP 2. M.U.T.-III data list

  • Refer to Data List Reference Table .

  1. Item 05: Intake air temperature sensor
  2. Item 06: Engine coolant temperature sensor
  3. Item 08: Manifold absolute pressure sensor
  4. Item 10: Air flow sensor
  5. Item 11: Accelerator pedal position sensor (main)
  6. Item 12: Accelerator pedal position sensor (sub)
  7. Item 13: Throttle position sensor (main)
  8. Item 15: Throttle position sensor (sub)
  9. Item BB: Barometric pressure sensor

Q. Are the check results normal?
Go to Step 3 .
Perform the diagnosis code classified check procedure for the sensor that has shown an abnormal data value (Refer to Inspection Chart for Diagnosis Code ).

STEP 3. M.U.T.-III data list

  • Refer to Data List Reference Table .

  1. Item 83: Power steering fluid pressure switch
  2. Item 87: Neutral switch

Q. Are the check results normal?
Go to Step 4 .
Perform the diagnosis code classified check procedure for the sensor that has shown an abnormal data value (Refer to Inspection Chart for Diagnosis Code ).

STEP 4. Check air intake from intake hose and inlet manifold.

Q. Is the check result normal?
Go to Step 5 .
Repair.

STEP 5. Check timing mark on the timing belt.

Q. Is the check result normal?
Go to Step 6 .
Align the timing marks.

STEP 6. Check throttle body (throttle valve portion) contamination.

Q. Is the check result normal?
Go to Step 7 .
Clean throttle body (throttle valve portion) (Refer to ).

STEP 7. M.U.T.-III data list

  • Refer to Data List Reference Table .

  1. Item AC: Right bank oxygen sensor (front)
  2. Item AD: Right bank oxygen sensor (rear)
  3. Item AE: Left bank oxygen sensor (front)
  4. Item AF: Left bank oxygen sensor (rear)

Q. Are the check results normal?
Go to Step 8 .
Perform the diagnosis code classified check procedure for the sensor that has shown an abnormal data value (Refer to Inspection Chart for Diagnosis Code ).

STEP 8. Perform voltage measurement at B-29 engine-ECU connector.

  • Disconnect engine-ECU connector, and connect special tool power plant ECU check harness (MB992110) to measure at connector for inspection.
  • Engine: Idle operation after warm-up
  • Transmission: P range
  • Radiator fan: Not operated
  • Voltage between terminal No. 60 and earth.
OK: Voltage increases when the headlamps are extinguished→illuminated

Q. Is the check result normal?
Go to Step 12 .
Go to Step 9 .

STEP 9. Connector check: B-29 engine-ECU connector and B-14 alternator connector

Q. Are the check results normal?
Go to Step 10 .
Repair or replace the connector.

STEP 10. Check harness between B-29 (terminal No. 60) engine-ECU connector and B-14 (terminal No. 1) alternator connector.

  • Check output line for open/short circuit and damage.

Q. Is the check result normal?
Go to Step 11 .
Repair the damaged harness wire.

STEP 11. Check the trouble symptom.

Q. Does the trouble symptom persist?
Replace the alternator.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

STEP 12. Visual check of ignition spark.

  • Remove the spark plug and install it to the ignition coil.
  • Connect the ignition coil connector.
  • Remove all injector connector.
  • At the engine start, check each spark plug produces a spark.

Q. Is the check result normal?
Go to Step 14 .
Go to Step 13 .

STEP 13. Check spark plug.

  • Check spark plug itself (Refer to GROUP 16 - Ignition System - On-vehicle Service - Spark Plug Check and Cleaning ).

Q. Is the check result normal?
Check ignition circuit system (Refer to Inspection Procedure 22 ).
Replace the spark plug.

STEP 14. Check purge control solenoid valve itself.

  • Check purge control solenoid valve itself (Refer to GROUP 17 - Emission Control - Evaporative Emission Control System - Purge Control Solenoid Valve Check ).

Q. Is the check result normal?
YES : Go to Step 15 <Except vehicles for Russia> .
YES : Go to Step 16 <Vehicles for Russia> .
Replace the purge control solenoid valve.

STEP 15. Check exhaust gas recirculation valve itself.

  • Check exhaust gas recirculation valve itself (Refer to GROUP 17 - Emission Control - Exhaust Gas Recirculation Valve - Exhaust Gas Recirculation Valve (Stepper Motor) Check ).

Q. Is the check result normal?
Go to Step 16 .
Replace the exhaust gas recirculation valve.

STEP 16. Check injector for spray condition.

  • Check each injector for spray condition (Refer to ).

Q. Is the check result normal?
Go to Step 17 .
Replace the injector.

STEP 17. Check compression pressure.

  • Check the compression pressure (Refer to GROUP 11C - On-vehicle Service - Compression Pressure Check ).

Q. Is the check result normal?
Go to Step 18 .
Repair.

STEP 18. Replace the engine-ECU.

  • After the engine-ECU has been replaced, check for the trouble symptom again.

Q. Does the trouble symptom persist?
Check for foreign matters (water, kerosene, etc.) in fuel and replace if necessary.
Check end.