P0304 Cylinder 3 Misfire Detected

Have you ever experienced your car engine idling rough, stalling, or exhibiting a loss of power while driving?

If you have, then you know how frustrating it can be, and how much it can disrupt your daily routine. One of the most common culprits of engine problems is a misfire in one of the cylinders. In this article, we will discuss everything you need to know about the P0304 code, which indicates a cylinder 3 misfire detected.

What is a Cylinder 3 Misfire?

Before we delve into the specifics of the P0304 code, let’s first understand what a cylinder misfire is. A cylinder misfire occurs when one of the engine cylinders fails to ignite properly. This can occur for a variety of reasons, such as a faulty spark plug, a damaged ignition coil, or a clogged fuel injector. When this happens, the engine will run rough, produce a noticeable loss of power, and may even stall.

What Causes a Cylinder 3 Misfire?

The P0304 code specifically refers to a misfire in cylinder 3. The most common causes of a cylinder 3 misfire include a faulty spark plug, a damaged ignition coil, a clogged fuel injector, or a vacuum leak. Other less common causes may include a malfunctioning EGR valve or a faulty engine control module (ECM).

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How is the P0304 Code Diagnosed?

Diagnosing the P0304 code requires a thorough inspection of the engine components. This includes checking the spark plugs, ignition coils, and fuel injectors for damage or wear.

Additionally, a vacuum leak test may be performed to determine if there is a leak in the engine’s vacuum system.

Finally, a diagnostic scan tool may be used to read the ECM for any stored fault codes.

What are the Symptoms of a Cylinder 3 Misfire?

The symptoms of a cylinder 3 misfire are similar to those of a general misfire in the engine. These can include a rough idle, a loss of power while driving, and even stalling.

You may also notice that the engine runs rough when accelerating or cruising at highway speeds. Additionally, the check engine light may illuminate, and the ECM may store a diagnostic trouble code (DTC) for the cylinder 3 misfire.

How is a Cylinder 3 Misfire Repaired?

Repairing a cylinder 3 misfire requires identifying the root cause of the problem.

This may involve replacing the spark plug, ignition coil, or fuel injector, depending on the cause of the misfire. In some cases, a vacuum leak may need to be repaired, or the ECM may need to be replaced. Once the root cause of the misfire is resolved, the engine should run smoothly again.


In summary, a cylinder 3 misfire can cause a lot of headaches for drivers. Fortunately, diagnosing and repairing the problem is relatively straightforward. By identifying the root cause of the misfire and replacing any faulty components, you can get your engine running smoothly again. If you suspect a cylinder misfire in your vehicle, it is important to have it diagnosed and repaired as soon as possible to prevent further damage to the engine.


  1. Can a cylinder misfire be caused by a faulty oxygen sensor?

No, a faulty oxygen sensor typically does not cause a cylinder misfire.

  1. Can a cylinder misfire cause damage to the engine?

Yes, a cylinder misfire can cause damage to the engine over time if left untreated.

  1. Is it safe to continue driving with a cylinder misfire?

No, it is not safe to drive with a cylinder misfire. Continuing to drive with a misfire can cause damage to the engine and may result in costly repairs.

  1. Can a cylinder misfire be fixed at home?

It is possible to repair a cylinder misfire at home, but it is recommended to have it diagnosed by a professional mechanic first to ensure that the correct components are replaced.

  1. How often should spark plugs be replaced?

Spark plugs should be replaced every 30,000 to 100,000 miles, depending on the make and model of the vehicle.