Inspection Procedure 8: Unstable Idling (Rough Idling, Hunting), Improper Idling Speed (Too High or too Low), Engine Stalls during Idling (Die Out)

COMMENT ON TROUBLE SYMPTOM

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

PROBABLE CAUSE

Failed ignition system
Failed fuel system
Failed throttle valve control system
Failed air-fuel control system
Failed intake/exhaust system
Failed emission gas cleaning system
Contamination of throttle body (throttle valve portion)
Timing belt in out of place
Improper compression pressure
Failed engine-ECU <M/T>
Failed engine-A/T-ECU <A/T>

DIAGNOSIS PROCEDURE

STEP 1. Check battery condition.

Q. Has the battery terminal been disconnected?

	After warm-up engine, idle for about 10 minutes.

	Go to Step 2 .

STEP 2. M.U.T.-III diagnosis code

Q. Diagnosis code set?

	Inspection chart for diagnosis code (Refer to ).

	Go to Step 3 .

STEP 3. M.U.T.-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 (sub)
Item 21: Engine coolant temperature sensor
Item 29: Inhibitor switch <A/T>
Item 77: Accelerator pedal position sensor (sub)
Item 78: Accelerator pedal position sensor (main)
Item 79: Throttle position sensor (main)
Item B4: Power steering fluid pressure sensor

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. M.U.T.-III data list

Refer to Data List Reference Table .

Item 25: Barometric pressure sensor

Q. Are the check results normal?

	Go to Step 5 .

	Replace engine-ECU <M/T> or engine-A/T-ECU <A/T>.

STEP 5. Check air intake from intake hose and inlet manifold.

Q. Is the check result normal?

	Go to Step 6 .

	Repair.

STEP 6. Check timing marks of timing belt.

Q. Is the check result normal?

	Go to Step 7 .

	Align timing marks.

STEP 7. Check throttle body (throttle valve portion) contamination.

Q. Is the check result normal?

	Go to Step 8 .

	Clean throttle body (throttle valve portion) (Refer to ).

STEP 8. M.U.T.-III data list

Refer to Data List Reference Table .

Item 11: Cylinder 1, 4 oxygen sensor
Item 39: Cylinder 2, 3 oxygen sensor

Q. Are the check results normal?

	Go to Step 9 .

	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 9. Perform voltage measurement at C-111 engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector.

Measure engine-ECU <M/T> or engine-A/T-ECU <A/T> terminal voltage.
Engine: Idling after warm-up
Transmission: Neutral <M/T> or P range <A/T>
Radiator fan: Not operating
Voltage between terminal No. 45 and earth.

OK: Switching the headlamps to ON from OFF causes the voltage to increase.

Q. Is the check result normal?

Go to Step 13 .

Go to Step 10 .

STEP 10. Connector check: C-111 engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector and B-119 alternator connector

Q. Is the check result normal?

Go to Step 11 .

Repair or replace.

STEP 11. Check harness between C-111 (terminal No. 45) engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector and B-119 (terminal No. 1) alternator connector.

note

Before checking harness, check intermediate connector B-17, and repair if necessary.

Check output line for open/short circuit and damage.

Q. Is the check result normal?

Replace alternator. Then go to Step 12 .

Repair.

STEP 12. Check trouble symptom

Q. Does trouble symptom persist?

	Replace engine-ECU <M/T> or engine-A/T-ECU <A/T>.

	Check end.

STEP 13.Check spark plug

Q. Is the check result normal?

	Go to Step 14 .

	Replace spark plug.

STEP 14. Check ignition coil spark.

Q. Is the check result normal?

	Go to Step 15 .

	Check ignition circuit system (Refer to Inspection Procedure 26 ).

STEP 15. Check purge control solenoid valve itself.

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

Q. Is the check result normal?

	Go to Step 16 .

	Replace purge control solenoid valve.

STEP 16. Check EGR valve (stepper motor) itself.

Check EGR valve (stepper motor) itself [Refer to GROUP 17 - Emission Control System - Exhaust Gas Recirculation (EGR) System - EGR Valve (Stepper Motor) Check ].

Q. Is the check result normal?

	Go to Step 17 .

	Replace EGR valve (stepper motor).

STEP 17. Check injector for spray condition.

Check each injector for spray condition (Refer to ).

Q. Is the check result normal?

	Go to Step 18 .

	Replace injector.

STEP 18. Check compression pressure.

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

Q. Is the check result normal?

	Go to Step 19 .

	Repair.

STEP 19. Replace engine-ECU <M/T> or engine-A/T-ECU <A/T>.

After engine-ECU <M/T> or engine-A/T-ECU <A/T> is replaced, re-check for trouble symptom.

Q. Does trouble system persist?

	Check for foreign matters (water, kerosene, etc.) in fuel and replace if necessary.

	Check end.