Inspection Procedure 14
Inspection procedure 14: Hesitation, sag, stumble, poor acceleration or surgeCOMMENT
- Defective ignition system, abnormal air/fuel ratio, poor compression pressure, etc. are suspected.
TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Malfunction of the fuel pump system [California].
- Malfunction of the ignition system.
- Poor compression.
- Malfunction of the EGR system [California].
- Improper operation of the PCV valve.
- Vacuum leak.
- Clogged air cleaner.
- Clogged exhaust system.
- Increased resistance to the transmission drive
- 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
NOTE: To protect the CVT, the TCM outputs, into the ECM, the request signal to reduce the engine torque according to the operation condition. Based on the signal, the ECM closes the throttle valve, retards the ignition or carries out fuel cut. At that time, the engine output seems to temporarily reduce, but there is no malfunction. [CVT]
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 Diagnostic Trouble Code Chart. Diagnostic Trouble Code Descriptions
NO : Go to Step 3. [CVT]
NO : Go to Step 4. [M/T]
STEP 3. Using scan tool MB991958, read the diagnostic trouble code (DTC).
NOTE: When the CVT has a malfunction, the TCM might output the request signal of reducing the engine torque in order to protect the CVT.
1. Turn the ignition switch to the "ON" position.
2. Read the TCM-DTC.
3. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the TCM-DTC set?
YES : Refer to Diagnosis - Diagnostic Trouble Code Chart. Diagnostic Trouble Code Descriptions
NO : Go to Step 4.
STEP 4. Using scan tool MB991958, check actuator test item 01: injector.
1. Turn the ignition switch to the "ON" position.
2. Test Reference Table. Actuator Test Reference Table
a. Item 01: Injector.
3. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Are thy operating properly?
YES : Go to Step 5.
NO : Repair or replace it. Then confirm that the malfunction symptom is eliminated.
STEP 5. Check the ignition timing.
1. Refer to On-vehicle Service - Ignition Timing Check. Testing and Inspection
Q: Is the ignition timing normal?
YES : Go to Step 6.
NO : Check for installed conditions of the timing chain. Then confirm that the malfunction symptom is eliminated.
STEP 6. Using scan tool MB991958, check data list and actuator test.
1. Turn the ignition switch to the "ON" position.
2. Check the following items in the data list. Refer to Data List Reference Table. Datal List Reference Table
a. Item 05: Intake Air Temperature Sensor.
b. Item 06: Engine Coolant Temperature Sensor.
c. Item 13: Throttle Position Sensor (main).
d. Item 15: Throttle Position Sensor (sub).
e. Item 11: Accelerator Pedal Position Sensor (main).
f. Item 12: Accelerator Pedal Position Sensor (sub).
3. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Are they operating properly?
YES : Go to Step 7.
NO : Repair or replace it. Then confirm that the malfunction symptom is eliminated.
STEP 7. Check the fuel pressure.
Refer to Fuel Pressure Test. Testing and Inspection
Q: Is the fuel pressure normal?
YES : Go to Step 8.
NO : Repair or replace it. Then confirm that the malfunction symptom is eliminated.
STEP 8. Check the spark plugs.
Refer to Ignition System - On-vehicle service - Spark Plug Check. 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 9.
STEP 9. Check the ignition coil.
Refer to Ignition System - On-vehicle service - Ignition Coil Check. 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 10.
STEP 10. Check the positive crankcase ventilation system.
Refer to Emission Control System - Positive Crankcase Ventilation System Check. System Check
Q: Is the positive crankcase ventilation system?
YES : Check the following items, and repair or replace the defective items.
a. Vacuum leak.
b. Clogged air cleaner.
c. Clogged exhaust system.
d. Check if fuel is contaminated.
e. Check if the injectors are clogged.
f. Check if the foreign materials (water, kerosene, etc.) got into fuel.
Then confirm that the malfunction symptom is eliminated.
NO : Repair it. Then confirm that the malfunction symptom is eliminated.