Inspection Procedure 10: Hesitation, Sag, Poor Acceleration, Stumble or Surge


COMMENTS ON TROUBLE SYMPTOM



  • The failure could possibly be caused by the failed ignition system, improper air-fuel ratio, faulty compression pressure and so on.

PROBABLE CAUSES



  • Failed air-fuel ratio control system
  • Failed ignition system
  • Failed fuel system
  • Failed intake and exhaust air system
  • Failed electronic-controlled throttle valve system
  • Contamination around the throttle valve
  • Improper compression pressure
  • Failed CVT
  • Failed engine-ECU

DIAGNOSIS PROCEDURE
note To protect the CVT, the CVT-ECU outputs, into the engine-ECU, the request signal to reduce the engine torque according to the operation condition. Based on the signal, the engine-ECU 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.

STEP 1. M.U.T.-III diagnosis code

Q. Is diagnosis code set?
Inspection chart for diagnosis code (Refer to ).
NO : Go to Step 2.

STEP 2. M.U.T.-III diagnosis code
note When the CVT has a malfunction, the CVT-ECU might output the request signal of reducing the engine torque in order to protect the CVT.

  • Confirm the diagnosis code is set from CVT-ECU.

Q. Is the diagnosis code set?
Perform troubleshooting of CVT System (Refer to GROUP 23A - Diagnosis Code Chart ).
Go to Step 3.

STEP 3. Check injector for operating sound.

  • Injector check (Refer to ).

Q. Is operating sound audible?
Go to Step 4.
Check the injector system of the defective cylinder. Check code No. P0261: No. 1 injector circuit low input (Refer to ). Check code No. P0262: No. 1 injector circuit high input (Refer to ). Check code No. P0264: No. 2 injector circuit low input (Refer to ). Check code No. P0265: No. 2 injector circuit high input (Refer to ). Check code No. P0267: No. 3 injector circuit low input (Refer to ). Check code No. P0268: No. 3 injector circuit high input (Refer to ). Check code No. P0270: No. 4 injector circuit low input (Refer to ). Check code No. P0271: No. 4 injector circuit high input (Refer to ).

STEP 4. M.U.T.-III data list

  • Data list reference table (Refer to ).

  1. Item 5: Intake air temperature sensor
  2. Item 6: Engine coolant temperature sensor
  3. Item 11: Accelerator pedal position sensor (main)
  4. Item 12: Accelerator pedal position sensor (sub)
  5. Item 13: Throttle position sensor (main)
  6. Item 15: Throttle position sensor (sub)
  7. Item BB: Barometric pressure sensor

Q. Are the check results normal?
Go to Step 5.
Perform the diagnosis code classified check procedure for the sensor that has shown an abnormal data value. Inspection chart for diagnosis code (Refer to ).

STEP 5. Check purge control solenoid valve itself.

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

Q. Is the check result normal?
Go to Step 6.
Replace the purge control solenoid valve.

STEP 6. M.U.T.-III data list

  • Data list reference table (Refer to ).

  1. Item AC: Oxygen sensor (front)
  2. Item AD: Oxygen sensor (rear)

Q. Are the check results normal?
Go to Step 7.
Perform the diagnosis code classified check procedure for the sensor that has shown an abnormal data value. Inspection chart for diagnosis code (Refer to ).

STEP 7. Visual check of ignition spark.

  • Remove the spark plug and install it to the ignition coil.
  • Connect the ignition coil connector.
  • Disconnect all injector connectors.
  • At the engine start, check each spark plug produces a spark.

Q. Is the check result normal?
Go to Step 8.
Check Inspection Procedure - ignition circuit system (Refer to ).

STEP 8. Check throttle body (throttle valve portion) contamination.

Q. Is the check result normal?
Go to Step 9.
Throttle body (throttle valve area) cleaning (Refer to ).

STEP 9. Check compression pressure.

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

Q. Is the check result normal?
Go to Step 10.
Repair.

STEP 10. Fuel pressure measurement.

  • Fuel pressure test (Refer to ).

Q. Is the check result normal?
Go to Step 11.
Repair.

STEP 11. Check air intake from inlet hose and inlet manifold.

Q. Is the check result normal?
Go to Step 12.
Repair.

STEP 12. Check exhaust leak from exhaust manifold.

Q. Is the check result normal?
Replace the engine-ECU.
Repair.