P0309 Cylinder 8 Misfire Detected

Have you ever experienced a sudden jolt in your car while driving? It could be a sign of a misfire. One of the most common causes of a misfire is a problem with the cylinder, specifically cylinder 8. In this article, we will discuss everything you need to know about P0309: Cylinder 8 Misfire Detected.

Understanding What P0309 Means

When the check engine light in your car comes on, it can be concerning. One of the most common reasons why the check engine light comes on is because of a misfire. Specifically, P0309 means that the engine control module (ECM) has detected a misfire in cylinder 8.

Causes of Cylinder 8 Misfire

There are numerous reasons why cylinder 8 misfire could occur. Some of the most common reasons include:

  1. Faulty Spark Plugs

Spark plugs play a crucial role in the ignition system. They are responsible for creating a spark that ignites the fuel in the cylinder. If the spark plugs are faulty, they can cause a misfire in cylinder 8.

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  1. Ignition Coil Failure

The ignition coil is another crucial component of the ignition system. It is responsible for supplying power to the spark plugs. If the ignition coil fails, it can cause a misfire in cylinder 8.

  1. Fuel Injector Issues

Fuel injectors are responsible for delivering fuel to the cylinders. If there is an issue with the fuel injector in cylinder 8, it can cause a misfire.

  1. Low Compression

Low compression is another common cause of a misfire. It occurs when the pressure in the cylinder is too low, which can make it difficult for the fuel to ignite.

Diagnosing P0309

Diagnosing P0309 can be challenging, as there are numerous potential causes. To determine the cause of the misfire, a mechanic will typically perform a series of tests. These tests may include a compression test, fuel pressure test, and spark plug test.

Fixing P0309

Once the cause of the misfire has been identified, the mechanic will be able to provide a recommendation for repair. In some cases, the fix may be as simple as replacing a faulty spark plug. In other cases, the repair may be more complex, such as replacing the ignition coil or fuel injector.

Preventing Cylinder 8 Misfire

Preventing cylinder 8 misfire can help you avoid costly repairs down the road. One of the best ways to prevent misfires is to keep up with regular maintenance. This includes replacing spark plugs and other components as recommended by the manufacturer.


P0309: Cylinder 8 Misfire Detected can be a frustrating problem to deal with. However, by understanding the causes and symptoms of a misfire, you can take steps to prevent it from happening in the future. If you are experiencing a misfire, don’t hesitate to take your car to a mechanic for diagnosis and repair.


  1. What are the symptoms of a misfire in cylinder 8?

The symptoms of a misfire in cylinder 8 can include a rough idle, loss of power, and a check engine light.

  1. Can a misfire damage your engine?

Yes, a misfire can cause damage to your engine over time if left unresolved.

  1. How long can you drive with a misfire?

It is not recommended to drive with a misfire, as it can cause damage to your engine. If you are experiencing a misfire, it’s best to take your car to a mechanic as soon as possible.

  1. Can a misfire fix itself?

No, a misfire will not fix itself. It’s important to address the issue as soon as possible to prevent further damage.

  1. How much does it cost to fix a misfire?

The cost of fixing a misfire can vary depending on the cause of the problem. In some cases, a simple repair like replacing a spark plug may only cost a few hundred dollars. In other cases, more complex repairs like replacing an ignition coil or fuel injector could cost upwards of $1,000.