P0306 Cylinder 5 Misfire Detected

When it comes to car trouble, a misfire in your engine can be one of the most frustrating things to deal with. If you’ve gotten a code reading of P0306, it means that your engine’s computer has detected a misfire in Cylinder 5.

This can be caused by a number of things, from something as simple as a bad spark plug to more serious issues like a failing fuel injector or a blown head gasket. In this article, we’ll take a closer look at what P0306 means, what can cause it, and what steps you can take to fix the problem.

What is Cylinder 5 Misfire Detected (P0306)?

P0306 is a diagnostic trouble code that indicates a misfire in Cylinder 5 of your engine. The “P” stands for Powertrain, which includes the engine, transmission, and other related components. The “0306” refers specifically to Cylinder 5, which is one of the cylinders in your engine that helps to turn the crankshaft and power your vehicle.

When your engine is running smoothly, each cylinder fires in a specific order. If a cylinder misfires, it means that something has gone wrong with that cycle. This can cause a number of problems, including reduced power, decreased fuel efficiency, rough idling, and engine damage over time.

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What Causes Cylinder 5 Misfire Detected (P0306)?

There are a number of things that can cause a misfire in Cylinder 5. Some of the most common causes include:

  1. Faulty spark plug: A bad spark plug can cause a misfire in any cylinder. Over time, spark plugs can wear down, become dirty, or simply fail. If Cylinder 5’s spark plug is faulty, it can cause the misfire to occur.
  2. Failing ignition coil: The ignition coil is responsible for delivering electrical current to the spark plug. If it fails, it can cause a misfire in the corresponding cylinder.
  3. Clogged fuel injector: If the fuel injector for Cylinder 5 is clogged or dirty, it can cause a lean fuel mixture or a fuel-rich mixture, both of which can lead to a misfire.
  4. Vacuum leak: A vacuum leak can cause lean fuel conditions or reduce the amount of air available for combustion, leading to a misfire.
  5. Low compression: If Cylinder 5 has low compression, it may not be able to fire properly, leading to a misfire.

How to Fix Cylinder 5 Misfire Detected (P0306)?

The first step in fixing a misfire in Cylinder 5 is to determine the underlying cause. Here are some steps you can take:

  1. Check the spark plug: Pull the spark plug for Cylinder 5 and inspect it for wear, damage, or buildup. If it looks dirty or worn out, replace it with a new one.
  2. Check the ignition coil: Use a multimeter to test the ignition coil for Cylinder 5. If it’s not delivering the proper voltage, it may need to be replaced.
  3. Check the fuel injector: Use a fuel pressure gauge to check the fuel pressure for Cylinder 5. If it’s too low, the fuel injector may be clogged or dirty and will need to be cleaned or replaced.
  4. Check for vacuum leaks: Use a smoke machine or carburetor cleaner to check for vacuum leaks around the intake manifold and hoses.
  5. Check compression: Use a compression tester to check the compression for Cylinder 5. If it’s too low, you may need to replace the head gasket or perform other engine repairs.


If you’re experiencing a misfire in Cylinder 5, don’t panic. With the right tools and a little bit of knowledge, you can diagnose and fix the problem yourself. Remember to check the spark plug, ignition coil, fuel injector, vacuum system, and compression to determine the underlying cause. Once you’ve found the problem, you can take steps to fix it and get your engine running smoothly again.


  1. Can I still drive my car with a Cylinder 5 misfire?

It’s not recommended to drive your car with a misfire, as it can cause damage to your engine over time. It’s best to diagnose and fix the problem as soon as possible.

  1. How much does it cost to fix a Cylinder 5 misfire?

The cost of fixing a misfire can vary depending on the underlying cause. Replacing a spark plug can cost as little as $10, while a failed fuel injector or ignition coil can cost several hundred dollars.

  1. How long does it take to fix a Cylinder 5 misfire?

The time it takes to fix a misfire can vary depending on the underlying cause. Simple fixes like replacing a spark plug can take just a few minutes, while more complex repairs like replacing a head gasket can take several hours.

  1. Can a misfire cause damage to my engine?

Yes, if left untreated, a misfire can cause damage to your engine over time. It’s best to diagnose and fix the problem as soon as possible to avoid further damage.

  1. How can I prevent Cylinder 5 misfires in the future?

Regular engine maintenance, including changing the spark plugs, fuel filter, and air filter, can help prevent misfires from occurring. It’s also important to address any issues as soon as they arise.