Inspection Procedure 8
COMMENT- In cases such as the above, the cause is probably the air/fuel mixture or idle air control motor. Other systems affecting idle quality include the ignition system and compression.
TROUBLESHOOTING HINTS
The most likely causes for this case:
- Malfunction of the ignition system.
- Malfunction of air/fuel ratio control system.
- Malfunction of the IAC system.
- Malfunction of the evaporative emission purge solenoid system.
- Poor compression.
- Vacuum leak.
- Malfunction of the EGR solenoid system.
DIAGNOSIS
Required Special Tools:
MB991502: Scan Tool (MUT-II)
STEP 1. Check if the battery terminal is disconnected
Has the battery terminal been disconnected lately?
If no, go to Step 2.
If yes, start the engine and let it run at idle for approximate 10 minutes after engine warm up. Then, if a malfunction occurs, go to Step 2.
CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.
STEP 2. Using scan tool MB991502, read the diagnostic trouble code (DTC).
If DTC is not output, go to Step 3.
If DTC is output, refer to Diagnostic Trouble Code Chart.
STEP 3. Check the engine idling state.
If hunting badly, go to Step 4.
If hunting is not too bad, go to Step 6.
STEP 4. Check the following items.
1. Carry out the following cleaning or adjustment.
a. Clean the throttle valve area
b. Check and adjust the fixed SAS <3.0L Engine>
2. After cleaning or adjusting, confirm that the malfunction symptom is eliminated.
If the malfunction symptom is not resolved, go to Step 5. If the malfunction symptom is resolved, the check is completed.
STEP 5. Check for vacuum leaks.
1. Check the following items, and repair or replace the detective items.
a. Broken intake manifold gasket.
b. Broken air intake hose.
c. Broken vacuum hose.
d. Positive crankcase ventilation valve does not operate.
Then confirm that the malfunction symptom is eliminated.
STEP 6. Check the idle air control (IAC) motor operation sound.
1. Check that the engine coolant temperature is 20° C (68° F) or below.
NOTE: Disconnecting the engine coolant temperature sensor connector and connecting the harness side of the connector to another engine coolant temperature sensor that is at 20°C (68°F) or below is also okay
2. Check the operation sound of the IAC motor can be heard after the ignition is switched "ON" (but without starting the engine).
- An operation sound should be heard.
If correct, go to Step 7.
If no sound is heard, refer to DTC P0505 - Idle Control System Malfunction <3.0L Engine> or refer to DTC P0505 - Idle Control System Malfunction <3.5L Engine>.
CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.
STEP 7. Using scan tool MB991502, check actuator test items 01, 02, 03, 04, 05, 06: Injector.
If the test items indicate a defect, go to Step 8.
If the test items do not indicate a defect, go to Step 11.
STEP 8. Check the power supply line at injector connectors A-70, A-71, A-72, A-73, A-74, A-75.
1. Disconnect connectors A-70, A-71, A-72, A-73, A-74, A-75 and measure at the harness side.
2. Turn the ignition switch "ON".
3. Measure current while connecting terminal 1 to ground via a 20-ohms resistor.
- Current should be 0.5 ampere or more.
4. Turn the ignition switch "OFF".
If 0.5 ampere or more, go to Step 9.
If less than 0.5 ampere, check intermediate connector A-04, and repair or replace if necessary. Refer to vehicle level Testing and Inspection. If intermediate connector A-04 is in good condition, repair the harness wire between MFI relay connector C-59 and injector connectors A-70, A-71, A-72, A-73, A-74, A-75. Then check that the malfunction is eliminated.
STEP 9. Check the circuits at PCM connector C-89.
1. Disconnect connector C-89 and measure at the harness side.
2. Disconnect PCM connector C-90. Using a jumper wire, connect terminal 49 to ground. Then operate the MFI relay.
3. Turn the ignition switch "ON".
4. Connect terminals 1, 2, 9, 10, 24, 25 to ground via a 20-ohms resistor to measure the current at each injector as follows:
Terminal 1 for the number 1 cylinder injector
Terminal 9 for the number 2 cylinder injector
Terminal 24 for the number 3 cylinder injector
Terminal 2 for the number 4 cylinder injector
Terminal 10 for the number 5 cylinder injector
Terminal 25 for the number 6 cylinder injector
- Current should be 0.3 ampere or more.
5. Turn the ignition switch "OFF".
If 0.3 ampere or more, go to Step 10.
If less than 0.3 ampere, check intermediate connector A-04. Repair or replace if necessary. Refer to vehicle level Testing and Inspection. If intermediate connector A-04 is in good condition, repair the harness wire between injector connectors A-70, A-71, A-72, A-73, A-74, A-75 and PCM connector C-89. Then check that the malfunction is eliminated.
STEP 10. Check harness connector C-89 at the PCM for damage.
If harness connector C-89 is in good condition, replace the injector.
If harness connector C-89 is damaged, repair or replace it. Refer to vehicle level Testing and Inspection.
Then check that the malfunction is eliminated.
CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.
STEP 11. Using scan tool MB991502, check data list and actuator test.
1. Check the following items in the data list.
Refer to Data List Reference Table.
a. Item 26: Closed Throttle Position Switch <3.0L Engine>.
b. Item 13: Intake Air Temperature Sensor.
c. Item 25: Barometric Pressure Sensor.
d. Item 21: Engine Coolant Temperature Sensor.
e. Item 59: Heated Oxygen Sensor (rear)
f. Item 11: Heated Oxygen Sensor (front)
g. Item 69: Left Bank Heated Oxygen Sensor (rear)
h. Item 39: Left Bank Heated Oxygen Sensor (front)
i. Item 27: Power Steering Pressure Switch.
j. Item 28: A/C Switch
k. Item 29: Park/neutral Position Switch
2. Check the following items in the actuator test.
Refer to Actuator Test Reference Table.
a. Item 08: Evaporative Emission Purge Solenoid.
b. Item 10: EGR Solenoid.
If the checks above meet the specifications, go to Step 12.
If the checks above do not meet the specifications, repair or replace. Then confirm that the malfunction symptom is eliminated.
CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.
STEP 12. Using scan tool MB991502, check data list.
1. Check the following items in the data list.
Refer to Data List Reference Table.
a. Item 45: Idle Air Control Motor Position.
If the check above meets the specification, go to Step 13. If the check above does not meet the specification, adjust the basic idle speed. Refer to Basic Idle Speed Adjustment. After adjusting, confirm that the malfunction symptom is eliminated.
CAUTION: To prevent damage to the scan tool, turn the ignition switch "OFF" before connecting or disconnecting the scan tool.
STEP 13. Using scan tool MB991502, check data list.
1. Check the following items of the data list. Refer to Data List Reference Table.
a. Item 11: Heated Oxygen Sensor (front)
b. Item 39: Left Bank Heated Oxygen Sensor (front)
- Voltage should fluctuate between 0 - 0.4 volts and 0.6 - 1 .0 volt while idling after the engine has been warmed.
If the voltage does not fluctuate, go to Step 14.
If the voltage fluctuates, go to Step 16.
STEP 14. Check the fuel pressure.
Refer to Fuel Pressure Test.
If correct, go to Step 15.
If incorrect, repair or replace. Then confirm that the malfunction symptom is eliminated.
STEP 15. Check the following items.
1. Check the following items, and repair or replace the defective items.
a. Vacuum leak.
- Broken intake manifold gasket.
- Broken air intake hose.
- Broken vacuum hose.
- Positive crankcase ventilation valve does not operate.
b. Injector clogged.
Then confirm that the malfunction symptom is eliminated.
STEP 16. Check the ignition timing.
Refer to On-vehicle Service <3.0L Engine>.
Refer to On-vehicle Service <3.5L Engine>.
If within specifications, go to Step 17.
If not within specifications, check that the crankshaft position sensor and timing belt cover are in the correct position. Then confirm that malfunction symptom is eliminated.
STEP 17. Check the following items.
1. Check the following items, and repair or replace the defective items.
a. Check the ignition coil, spark plugs, spark plug cables.
b. Check the purge control system.
c. Check compression.
d. Check it the foreign materials (water, kerosene, etc.) got into fuel.
e. Check the EGR control system.
Then confirm that the malfunction symptom is eliminated.