P0304
DTC P0304 CYLINDER 4-MISFIRE DETECTEDGENERAL DESCRIPTION
The Misfire monitor diagnostic is based on crankshaft rotation velocity variation. The PCM determines crankshaft rotational velocity using the crankshaft position sensor and camshaft position sensor. When a cylinder misfires the crankshaft slows down momentarily. By monitoring the crankshaft and camshaft position sensor signals, the PCM can calculate when a misfire occurs. For a non-catalyst damaging misfire, the diagnostic will be required to report a misfire present within 1000-3200 engine revolutions. For catalyst damaging misfire, the diagnostic will respond to monitor 200 engine revolutions. Rough roads may cause false misfire detection. The rough road(acceleration)sensor consists of a piezoelectric vibration pick up which detects vertical acceleration of the vehicle. The sensor signal is used by the PCM to determine the degree of vertical movement of the car, for example, on a bumpy road. Since this may also cause uneven engine running, the PCM uses the signal to distinguish the phenomenon from actual misfiring.
DTC DESCRIPTION
The PCM must monitor the engine for misfiring possibly caused by ignition coil defects or injector fails. If misfiring is detected, the PCM will identify the cylinder(s) that has(have) misfired and then calculate misfiring rate for a given duration. The DTC for Misfire (P0301. to 0304) is set as soon as the misfiring rate exceeds the limit which may result in damage to the catalyst or increase emissions. The PCM stores the individual DTC for a cylinder which has more than a 10% total misfire rate.
MONITOR DTC STATUS
NOTE: If any codes relating to injectors, HO2S, ECT(Engine Coolant Temperature) Sensor, Throttle Position sensor or Mass Air Flow Sensor are stored, do ALL REPAIRS associated with those codes before proceeding with this troubleshooting free.
1. Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode.
2. Press F4(DTAL) to select DTC information from the DTCs menu.
3. Confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.
4. Read "DTC Status" parameter.
5. Is parameter displayed "History(Not Present) fault"?
NOTE:
1. History (Not Present) fault: DTC occurred but has been cleared.
2. Present fault: DTC is occurring at present time.
YES: Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for loose or poor connections, bending, corrosion, contamination deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure
NO: Go to "Monitor Actuation Test" procedure.
MONITOR ACTUATION TEST
NOTE: The main purpose of this test is to identify potential engine mechanical condition problems and fuel and ignition systems problems that are not common to all cylinders. For best results, perform this test while maintaining as steady an rpm reading as possible.
Caution! Before beginning tests; set the parking brake, place gear selector in P or N and block drive wheels for safety.
1. Warm up the engine to normal operating temperature and let it idle.
2. Install Scan Tool and select "INJECTOR #1" parameter on the Actuation Test mode shown in the figure.
3. Monitor engine rpm and shut off the injector #1. by pressing "STRT(F1)" key
4. Repeat procedure on all injectors and record the engine rpm.
Specification : All cylinders should show an even RPM drop.
5. Was each cylinder's rpm drop within the same value?
YES: Go to "Timing Inspection" procedure.
NO: Cylinders with the least amount of RPM drop are not contributing their share of power.Go to "Spark plug cable Inspection" procedure.
NOTE: If the RPM loss between cylinders is quite large (200 RPM or more) and engine has high mileage, there is possibility of engine wear Perform compression test with pressure gauge to check the engine wear.
SPARK PLUG CABLE INSPECTION
1. Remove suspect cylinder's spark plug cable
2. Visually/physically inspect the following items:
- Damage, cracks and flashover
3. Measure the resistance of the spark plug cable referring to specification.
Specification : 5.6 kOhms/m ± 20%
NOTE: Resistance should not be higher than 10,000 Ohms per foot of cable. If resistance is higher than specification, replace the cable
4. Is the displayed value within the specified value?
YES: Go to "Spark Plug Inspection" procedure
NO: Repair as necessary and go to "Verification of Vehicle Repair" procedure.
SPARK PLUG CABLE INSPECTION
1. Remove suspect cylinder's spark plug cable.
2. Visually/physically inspect the following items:
1. Damage, cracks and flashover.
3. Measure the resistance of the spark plug cable referring to specification.
Specification : 5.6 kOhms/m ± 20%
NOTE: Resistance should not be higher than 10,000 Ohms per foot of cable. If resistance is higher than specification, replace the cable.
4. Is the displayed value within the specified value?
YES: Go to "Spark Plug Inspection" procedure.
NO: Repair as necessary and go to "Verification of Vehicle Repair" procedure.
SPARK PLUG INSPECTION
5. Remove suspect cylinder's spark plugs.
6. Visually/physically inspect the following items:
1. Damaged insulation, Worn electrodes, Oil or fuel fouled, Loose terminals and cracks.
2. Check for plug gap: 1.0 - 1.1 mm (0.039 - 0.043 in.)
3. Check if the spark plug for the relevant cylinder is lighter in color than the other plugs.
7. Was a problem found in any of the above areas?
YES: Repair as necessary and go to "Verification of Vehicle Repair" procedure.
NO: Go to "Fuel Injector Inspection" procedure.
FUEL INJECTOR INSPECTION
1. Check the fuel injectors for clogging or any restrictions.
Test Condition: Ignition "OFF"
Specification: No clogging and restriction
2. Is the fuel injector OK?
YES: Visually/physically inspect the engine mechanical problem as below:
1. Leaky or sticky valves or rings.
2. Excessive valve deposits.
3. Weak valve spring.
4. Leaking head gasket.
If NG, repair as necessary and go to "Verification of Vehicle Repair" procedure.
If OK, go to "Ignition Coil Inspection" procedure.
NO: Repair as necessary and go to "Verification of Vehicle Repair" procedure.
IGNITION COIL INSPECTION
1. Ignition "OFF".
2. Ignition coil connector: Disconnect.
3. Visually/physically inspect the following items:
1. Damage, cracks and flash over.
4. Measure the primary coil resistance between terminals 1 and 3
5. Is resistance within the specified value?
YES: Go to "Timing Inspection" procedure.
NO: Replace as necessary and go to "Verification of Vehicle Repair" procedure.
TIMING INSPECTION
6. Set up an oscilloscope as follows:
Channel A (+): terminal 2 of the CKPS, (-): ground
Channel B (+): terminal 2 of the CMPS, (-): ground
7. Start the engine and check for signal waveform whether synchronize with camshaft sensor or not and tooth is missing refer to sample waveforms as above.
8. Is the signal waveform normal?
YES: Go to "Air Leakage Inspection" procedure.
NO: Remove Crankshaft Position Sensor(CKPS) and calculate air gap between sensor and flywheel/torque converter.Readjust as necessary and go to next step.
NOTE: Air gap [0.3 - 1.7 mm [0.012 - 0.067 in] measure distance from housing to teeth on flywheel/torque converter (measurement "A") and from mounting surface on sensor to sensor tip (measurement "B") subtract "B" from "A".
- If fail to synchronize CKPS with CM PS, check that the crankshaft and camshaft are correctly aligned the matching marks of the pulleys. Repair or readjust as necessary and go to "Verification of Vehicle Repair" procedure.
AIR LEAKAGE INSPECTION
1. Visually/physically inspect the air leakage in intake/exhaust system as following items.
If OK, go to next step.
If NG, repair as necessary and go to "Verification of Vehicle Repair" procedure.
1. Vacuum hoses for splits, kinks and improper connections.
2. Throttle body gasket.
3. Gasket between intake manifold and cylinder head.
4. Seals between intake manifold and fuel injectors.
5. Exhaust system between HO2S and Three way catalyst for air leakage.
2. Was a problem found in any of the above areas?
YES: Go to "Fuel System Inspection" procedure.
NO: Repair air leakage and go to "Verification of Vehicle Repair" procedure.
FUEL SYSTEM INSPECTION
1. Check the fuel for excessive water, alcohol, or other contaminants. Replace contaminated fuel as necessary.
2. Install a fuel pressure gage.
3. Start engine and let it idle. Inspect fuel pressure with vacuum hose disconnected.
Test Condition: Ignition "ON" & Engine "ON" at Idle
Specification: 250 - 350 kPa(2.50 - 3.50 kg/sq.cm, 36 - 50 psi)
4. Is fuel pressure within the specified value?
YES: Check for poor connection between PCM and component: backed out terminal, improper mating, broken locks or poor terminal to wire connection. Repair as necessary and go to "Verification of Vehicle Repair" procedure.
NO: Repair as necessary refer 10 inspection noted as below and go to "Verification of Vehicle Repair" procedure.
NOTE:
1. Check if fuel line pressure decreases when accelerating quickly.
a. If it does, check fuel pump maximum pressure. If pressure is OK, check fuel line and filter for clogging.
2. If fuel pressure is lower than specification: Check for fuel line pressure while pinching fuel return hose.
a. If pressure quickly increases, check pressure regulator.
b. If pressure gradually increases, check for clogging between fuel pump and pressure regulator. If hose is not clogged, check fuel pump maximum pressure.
3. If fuel pressure is higher than specification: Is fuel line clogged?
a. If it is not, replace pressure regulator.
b. If it is, replace it.
VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.
1. Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode.
2. Press F4(DTAL) and confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.
3. Read "DTC Status" parameter.
4. Is parameter displayed "History(Not Present) fault"?
YES: System performing to specification at this time. Clear the DTC.
NO: Go to the applicable troubleshooting procedure.