Inspection Procedure 18
Inspection Procedure 18: Too High CO And HC Concentration When IdlingCOMMENT
- Abnormal air/fuel ratio is suspected.
TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Fuel pump system failed.
- Heated oxygen sensor failed.
- Ignition system failed.
- Poor compression.
- EGR system failed.
- Improper operation of the PCV valve.
- Evaporative emission control system failed.
- ECM failed.
DIAGNOSIS
Required Special Tool:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A
STEP 1. Check if the EGR valve sounds during initialization.
Q: Is the initialization sound heard in the EGR valve?
YES : Go to Step 2.
NO : Refer to Emission Control - Exhaust Gas Recirculation (EGR) System - EGR Valve (stepper motor) Check. [1][2]Component Tests and General Diagnostics
STEP 2. Using scan tool MB991958, read the diagnostic trouble code (DTC).
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Read the DTC.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is any DTC set?
YES : Refer to, Diagnostic Trouble Code Chart. Multiport Fuel Injection (MFI)
NO : Go to Step 3.
STEP 3. Check the ignition timing.
Refer to On-vehicle Service - Ignition Timing Check. Testing and Inspection
Q: Is the ignition timing normal?
YES : Go to Step 4.
NO : Check for installed conditions of the timing chain. Then confirm that the malfunction symptom is eliminated.
STEP 4. Using scan tool MB991958, check data list.
1. Turn the ignition switch to the "ON" position.
2. Check the following items in the data list. Refer to Data List Reference Table. Data List Reference Table
a. Item 5: Intake Air Temperature Sensor
b. Item 6: Engine Coolant Temperature Sensor
c. Item AD: Heated Oxygen Sensor (rear)
d. Item B1: Heated Oxygen Sensor (3rd) [Vehicles for California]
e. Item E1: Linear Air-fuel Ratio Sensor
3. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Are they operating properly?
YES : Go to Step 5.
NO : Repair or replace it. Then confirm that the malfunction symptom is eliminated.
STEP 5. Check the fuel pressure.
Refer to, Fuel Pressure Test. Testing and Inspection
Q: Is the fuel pressure normal?
YES : Go to Step 6.
NO : Repair it. Then confirm that the malfunction symptom is eliminated.
STEP 6. Check the spark plugs.
Refer to Ignition System - On-vehicle Service - Spark Plug Check and Cleaning. Testing and Inspection
Q: Are there any abnormalities?
YES : Replace the spark plug. Then confirm that the malfunction symptom is eliminated.
NO : Go to Step 7.
STEP 7. Check the ignition coil.
Refer to Ignition System - On-vehicle Service - Ignition Coil Check. Component Tests and General Diagnostics
Q: Are there any abnormalities?
YES : Replace the ignition coil. Then confirm that the malfunction symptom is eliminated.
NO : Go to Step 8.
STEP 8. Check the compression pressure.
Refer to On-vehicle Service - Compression Pressure Check. Testing and Inspection
Q: Is the compression pressure normal?
YES : Go to Step 9.
NO : Repair it. Then confirm that the malfunction symptom is eliminated.
STEP 9. Check the positive crankcase ventilation system.
Refer to Emission Control - Positive Crankcase Ventilation System - Crankcase Ventilation System Check. Crankcase Ventilation System Check
Q: Is the positive crankcase ventilation system normal?
YES : Go to Step 10.
NO : Repair it. Then confirm that the malfunction symptom is eliminated.
STEP 10. Check the evaporative emission control system.
Refer to Emission Control - Evaporative Emission Control System - Evaporative Emission Control System Check (purge flow check). Purge Control System Check
Q: Is the evaporative emission control system normal?
YES : Check the following item, and repair or replace the defective item.
a. Check if the injectors are clogged.
Then confirm that the malfunction symptom is eliminated.
NO : Repair it. Then confirm that the malfunction symptom is eliminated.