Inspection Procedure 17
Inspection Procedure 17: Too High CO And HC Concentration When IdlingCOMMENT
- Abnormal air/fuel ratio is suspected.
TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Malfunction of the fuel pump system.
- Malfunction of the ignition system.
- Poor compression.
- Malfunction of the EGR system
- Improper operation of the PCV valve.
- Malfunction of the ECM.
DIAGNOSIS
Required Special Tools:
- 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.
NOTE: Excluding the vehicle with the specification for California, go to Step 2.
Q: Is the initialization sound heard in the EGR valve?
YES : Go to Step 2.
NO : Refer to Emission Control - 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 MFI, Diagnostic Trouble Code Chart. Diagnostic Trouble Code Descriptions
NO : Go to Step 3.
STEP 3. Check the ignition timing.
Refer to Engine Mechanical, On-vehicle Service - Ignition Timing Check.
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 MFI, Data List Reference Table. Datal List Reference Table
a. Item 06: Engine Coolant Temperature Sensor.
b. Item 05: Intake Air Temperature 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. Datal List Reference Table
Q: Is the fuel pressure normal?
YES : Go to Step 6.
NO : Repair or replace 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.
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.
1. Remove the intake manifold.
2. Refer to Ignition System - On-vehicle service - Ignition Coil Check.
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 Engine Mechanical, On-vehicle service - Compression Pressure Check.
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 System - Positive Crankcase Ventilation System Check. PCV Valve Check
Q: Is the positive crankcase ventilation system?
YES : Go to Step 10.
NO : Repair it. Then confirm that the malfunction symptom is eliminated.
STEP 10. Check the purge control system.
Refer to Emission Control System - Purge Control System Check (Purge Flow Check). PCV Valve Check
Q: Is the purge control system normal?
YES : Check the following items, and repair or replace the defective items.
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.