P0304: Cylinder 4 Misfire Detected

The P0304 error code indicates that the engine control module (ECM) has detected a misfire in cylinder 4. A misfire occurs when a cylinder does not produce power, which can be due to issues with fuel, spark or compression.

Importance of addressing P0304

Addressing the P0304 error code is crucial because a misfiring cylinder can lead to various engine performance problems. Ignoring the issue can result in reduced fuel efficiency, increased emissions, and potential damage to the catalytic converter. Additionally, prolonged misfires can cause severe engine damage and costly repairs.

Can I safely drive my car with this error code?

While it is possible to drive your car with the P0304 error code, it is not recommended. Driving with a misfire can lead to further engine damage and potentially leave you stranded if the issue worsens. It is best to have the problem diagnosed and repaired as soon as possible to avoid more significant problems.

Common symptoms of P0304

• Check engine light is on
• Rough idle
• Lack of power and acceleration
• Poor fuel economy
• Engine hesitation during acceleration
• Smell of unburned fuel coming from the exhaust

Diagnosing P0304

Diagnosing the P0304 error code involves one or more of the following steps:

• OBD-II scanner: You or a mechanic will use an OBD-II scanner to retrieve the trouble code and any related codes.
• Visual inspection: The ignition system, including spark plugs, ignition coils, and wiring, is visually inspected for signs of wear or damage.
• Compression test: A compression test is performed on cylinder 4 to ensure it has adequate compression.
• Fuel system check: The fuel injectors and fuel pressure are tested to ensure they are functioning correctly.
• Leakdown test: A leakdown test may be performed to check for any issues with the cylinder head, valves or piston rings.

Repairing P0304

Repairing the P0304 error code typically involves one or more of the following steps:

• Replace spark plugs: Worn or fouled spark plugs in cylinder 4 should be replaced.
• Replace ignition coils: Faulty ignition coils should be replaced to ensure proper spark delivery.
• Repair or replace fuel injectors: Malfunctioning fuel injectors in cylinder 4 should be repaired or replaced.
• Fix compression issues: Any issues with compression, such as faulty valves or piston rings, should be repaired.
• Check and repair wiring: Damaged wiring or connectors related to the ignition and fuel systems should be repaired or replaced.
• Clear the code: After repairs, the mechanic will clear the code from the vehicle's computer and perform a test drive to ensure the issue is resolved.

Related reading

Follow the link below to reach our diagnostic check engine trouble codes catalog:
On-board diagnostics (OBD-II) trouble code directory