Code No. P0304: No. 4 Cylinder Misfire Detected










OPERATION



  • Refer to Code No. P0204: No. 4 Injector System .

FUNCTION



  • If a misfire occurs while the engine is running, the engine speed changes for an instant.
  • The engine-ECU checks for such changes in engine speed.

TROUBLE JUDGMENT


Check Conditions
  • Engine speed is 440 - 6,500 r/min.
  • Engine coolant temperature is higher than -10°C.
  • Barometric pressure is higher than 76 kPa.
  • Volumetric efficiency is 30 - 60 %.
  • Adaptive learning is complete for the vane which generates a crankshaft position signal.
  • While the engine is running, excluding gear shifting, deceleration, sudden acceleration/deceleration and A/C compressor switching.
  • The throttle deviation is -0.06 V/10 ms to +0.06 V/10 ms.
Judgment Criterion (change in the angular acceleration of the crankshaft is used for misfire detection).
  • Misfire has occurred more frequently than allowed during the last 200 revolutions [when the catalyst temperature is higher than 1,000°C].


  • Misfire has occurred in 15 or more of the last 1,000 revolutions (corresponding to 1.5 times the limit of emission standard).

PROBABLE CAUSES



  • Ignition system related part(s) failed
  • Failed No. 4 injector
  • Harness damage in No. 4 injector circuit
  • Low compression pressure
  • Failed engine-ECU

DIAGNOSIS PROCEDURE


STEP 1. Visual check of ignition spark.



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

Q. Is the check result normal?

Go to Step 3 .
Go to Step 2 .

STEP 2. Check spark plug.



  • Check spark plug (Refer to GROUP 16 - Ignition System - On-vehicle Service - Spark Plug Check and Cleaning ).

Q. Is the check result normal?

Check ignition circuit system (Refer to Inspection Procedure 22 ).
Replace the spark plug.

STEP 3. Connector check: B-106 No. 4 injector connector


Q. Is the check result normal?

Go to Step 4 .
Repair or replace the connector.

STEP 4. Check No. 4 injector itself.



  • Check No. 4 injector itself (Refer to ).

Q. Is the check result normal?

Go to Step 5 .
Replace the No. 4 injector.

STEP 5. Connector check: A-24X injector relay connector and B-29 engine-ECU connector


Q. Are the check results normal?

Go to Step 6 .
Repair or replace the connector.

STEP 6. Check harness between A-24X (terminal No. 3) injector relay connector and B-106 (terminal No. 1) No. 4 injector connector.


note Before checking harness, check intermediate connector A-13, and repair if necessary.

  • Check power supply line for damage.

Q. Is the check result normal?

Go to Step 7 .
Repair the damaged harness wire.

STEP 7. Check harness between B-106 (terminal No. 2) No. 4 injector connector and B-29 (terminal No. 19) engine-ECU connector



  • Check output line for damage.

Q. Is the check result normal?

Go to Step 8 .
Repair the damaged harness wire.

STEP 8. Check compression pressure.



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

Q. Is the check result normal?

Go to Step 9
Repair.

STEP 9. Check the trouble symptoms.


Q. Does trouble symptom persist?

Replace the engine-ECU.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).