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P0304: Cylinder #4 Misfire

Diagnosing your vehicle's problems can be difficult, but luckily most modern vehicles are equipped with an error code system. By using a special device, you can learn exactly what is wrong with your car. If you get an OBD-II scanner error code P0304 problem, it means one of the cylinders is not firing correctly. But do you know exactly what this means for your vehicle? Our guide will help you understand what you can do about this error code.

Check your Check Engine Light

Know What the Error Means

So what does the code P0304 mean? To understand what a cylinder misfiring means, you need to understand what the cylinders are. This is the part of the engine that actually produces the power. The cylinder down by an air-fuel mixture which is exploded by a spark, and the motion of the cyliders turns the crankshaft and eventually turns the wheels. This combustion is what is considered the cylinder “firing.” There are many different things that can cause the cylinder not to fire correctly. The error code simply tells you that it is misfiring, rather than why. A cylinder might fail to fire due to:

  • Faulty spark system
  • A fuel delivery problem
  • An exhaust gas recirculation malfunction
  • A large vacuum leak
  • A mechanical engine failure

The P0304 error code indicates that the number four cylinder specifically is failing to fire.

Symptoms To Look For

Any error code can be triggered by a faulty sensor. It can be useful to know what the symptoms of a real problem are, so you can tell whether something is seriously wrong or if the sensor just needs to be replaced. If your cylinder really is misfiring, your vehicle probably will suffer these symptoms:

  • Poor performance
  • Shaking while the engine is on
  • Strange smelling emissions

The Potential Risk

A cylinder not firing correctly is a serious problem. It may lead to further engine damage if not addressed for a long time. However, the cause of this problem may cause other problems much sooner. If you do not fix whatever is causing the cylinder not to fire, it may cause serious and irreversible damage to your catalytic converter or engine, which are two of the most expensive parts to replace. Additionally, a car that is not firing on all cylinders may be inherently more dangerous to drive.

Possible Solutions

You are probably now wondering, “How do I fix trouble code P0304?” First things first, if your car is not experiencing any of the usual symptoms, you should check the sensors for faults and replace them if necessary. If that is not the issue, you will need to check the other usual causes.

Chances are extremely high that the cylinder if misfiring due to a faulty spark system. This is, by far, the most common cause for this issue. You should start by checking the spark plugs and replacing any that need it. If you are overdue to replace your spark plugs, you may want to replace them just to be safe. If that does not fix the problem, you should also check the ignition coil, spark plug wires, and spark plug boot.

You should then inspect the components that connect to the cylinders, such as the manifold, camshaft, and valves. There may be a crack in one of these parts that is causing fuel to not be injected properly, the vacuum to be compromised, or some other mechanical failure. If you discover a problem with any of these components, they will either need to be repaired or replaced, which can be a difficult job. If you are not completely confident in your ability, you should take your vehicle to a mechanic.

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