Inspection Procedure 12: Hesitation, Sag, Poor Acceleration, Stumble, Surge

COMMENT ON TROUBLE SYMPTOM

Failure is possibly caused by failed ignition system, improper air-fuel ratio, throttle valve opening control system improper compression pressure or other faults.

PROBABLE CAUSES

Failed air-fuel ratio control system
Failed ignition system
Failed fuel system
Failed intake and exhaust system
Failed emission control system
Failed throttle valve control system
Throttle valve fouled around
Improper compression pressure
Failed engine-ECU

DIAGNOSIS PROCEDURE

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

Q. Diagnosis code set?

	Inspection chart for diagnosis code (Refer to ).

	Go to Step 2 .

STEP 2. Check injector for operating sound.

Check injector for operating sound (Refer to ).

Q. Can operating sound be heard?

	Go to Step 3 .

	Check the injector system of the defective cylinder. (Refer to Code No. P0201: No. 1 Injector System ). (Refer to Code No. P0202: No. 2 Injector System ). (Refer to Code No. P0203: No. 3 Injector System ).

STEP 3. M.U.T.-III data list

Refer to Data List Reference Table .

Item No. 6: Intake air temperature sensor
Item No. 8: Engine coolant temperature sensor
Item No. 11: Accelerator pedal position sensor (main)
Item No. 12: Accelerator pedal position sensor (sub)
Item No. 13: Throttle position sensor (main)
Item No. 14: Throttle position sensor (sub)

Q. Are the check results normal?

	Go to Step 4 .

	Perform the diagnosis code classified check Procedure for the sensor that has shown an abnormal data value (Refer to Inspection Chart for Diagnosis Code ).

STEP 4. Check purge control solenoid valve itself.

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

Q. Is the check result normal?

	Go to Step 5 .

	Replace purge control solenoid valve.

STEP 5. M.U.T.-III data list

Refer to Data List Reference Table .

Item No. 9: Oxygen sensor (front)
Item No. 10: Oxygen sensor (rear)

Q. Is the check result normal?

	Go to Step 6 .

	Perform the diagnosis code classified check Procedure for the sensor that has shown an abnormal data value (Refer to Inspection Chart for Diagnosis Code ).

STEP 6. Visual check of ignition spark.

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

Q. Is the check result normal?

	Go to Step 7 .

	Check ignition circuit system (Refer to Inspection Procedure 32 <134>, Inspection Procedure 33 <3A9>).

STEP 7. Check throttle body (throttle valve portion) for contamination.

Q. Is the check result normal?

	Go to Step 8 .

	Clean throttle body (throttle valve portion) (Refer to ).

STEP 8. Fuel pressure measurement.

Measure fuel pressure (Refer to ).

Q. Is the check result normal?

	Go to Step 9 .

	Repair the fuel pressure.

STEP 9. Check compression pressure.

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

Q. Is the check result normal?

	Replace the engine-ECU then perform the variant coding (Refer to GROUP 00 - Precautions Before Service - How to Perform Variant Coding ).

	Repair the compression pressure.