P0304 Cylinder 4 Four Misfire Detected (2025)

Technical Description

Cylinder #4 Misfire Detected

What does that mean?

This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to OBD-II equipped vehicles. Although generic, the specific repair steps may vary depending on make/model.

A P0304 code means that the the car's computer has detectedthat one of the engine's cylinders is not firing properly. In this case it'scylinder#4.

Symptoms

Symptoms may include:

  • the engine may be harder to start
  • the engine may stumble / stumble, and/or hesitate
  • other symptoms may also be present

Causes

A code P0304 may mean that one or more of the following has happened:

  • Faulty spark plug or wire
  • Faulty coil (pack)
  • Faulty oxygen sensor(s)
  • Faulty fuel injector
  • Burned exhaust valve
  • Faulty catalytic converter(s)
  • Running out of fuel
  • Poor compression
  • Defective computer

Possible Solutions

If there are no symptoms, the simplest thing to do is to reset the code andsee if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, checkall wiring and connectors that lead to the cylinders (i.e. spark plugs). Dependingon how long the ignition components have been in the car, it may be a goodidea to replace them as part of your regular maintenance schedule. I wouldsuggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable).Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalyticconverter has gone bad. If you smell rotten eggs in the exhaust, your cat converterneeds to be replaced. I've also heard in other cases the problems were faultyfuel injectors.

Other Reading

P0300 -Random/Multiple Cylinder Misfire Detected

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P0304 Cylinder 4 Four Misfire Detected (2025)

FAQs

P0304 Cylinder 4 Four Misfire Detected? ›

The P0304 code stands for “Cylinder 4 Misfire Detected”, which means your vehicle's cylinder 4 has misfired enough times for your powertrain control module (PCM) to notice. A worn spark plug, a faulty fuel injector, and a leaking valve are some possible causes of the P0304 code.

How do you fix a cylinder misfire P0304? ›

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.

How much does it cost to fix a P0304 code? ›

Considering the majority of reported P0304 error codes have been fixed by spark plug or coil replacement, the expected cost to resolve the issue should come in at around $100 - $300.

Can bad fuel injectors cause a P0304 code? ›

Yes, having bad fuel injectors will cause the code to appear in your car.

Can a cylinder 4 misfire fix itself? ›

Cars do not fix themselves. Misfires can damage catalytic converters and cause heat damage to valves and pistons. You'll have loss of power and horrible fuel economy. Leave it unrepaired for too long and it can destroy the engine.

Can I drive my car with a cylinder 4 misfire? ›

If left untreated, a cylinder misfire can lead to significant engine damage. Worse, if you experience a bad misfire while driving, it could result in an accident. This is why it's important to treat engine misfires as soon as you detect them.

Can low oil cause misfire? ›

Engine misfires are caused by many things, including: Dirty, broken or worn-out spark plugs. Low oil pressure (injector clogging) and/or overheating issues.

How long can I drive with a misfiring cylinder? ›

In most automobiles, you could theoretically travel thousands of miles with a misfiring cylinder. The engine's other cylinders will continue to produce power. So, even if you shake and stall along the wall (and don't acquire much speed or acceleration), the car will still operate.

Can dirty spark plugs cause misfire? ›

Worn or fouled spark plugs are one of the most common causes of engine misfires. These small but crucial components deliver the spark that ignites the fuel in your engine. If they're not working properly, your engine won't be firing on all cylinders.

What are the symptoms of a cylinder misfire? ›

Signs that an engine Is misfiring include slower acceleration or shaking during acceleration; the engine also might hesitate or briefly lose power. At idle, the engine might vibrate more than usual and run unevenly. Misfires can occur when an engine is cold or warm, and they can occur intermittently.

How serious is P0304? ›

The P0304 engine code can compromise your driving experience, so resolve the underlying cause (or causes) immediately. If your check engine light is on and the OBD-II scanner reads a P0304 code, use the guide below to address it.

Can a bad catalytic converter cause a P0304 code? ›

If it varies beyond 2 percent, the Monitor will set a P0304 code and illuminate the Check Engine Light. If there is more than a 10 percent variance, the Check Engine Light will blink or pulse in a steady manner to indicate that a harmful Catalytic Converter misfire is occurring.

What happens if you don't fix a cylinder misfire? ›

A misfire on its own does not usually signal a serious mechanical problem. Very often, it is just a spark plug, ignition coil or a fuel injector that needs to be replaced. However, if you ignore the problem, more cylinders could start to malfunction, possibly to the point that the engine stops working entirely.

What is the most likely cause of a cylinder misfire? ›

An engine misfire happens when the cylinders in the engine don't burn right or the combustion within the chamber is incomplete (or nonexistent!). Typically, engine misfires can be caused by a variety of factors, including malfunctioning coils, worn or faulty spark plugs, a leak or a faulty ignition switch.

Can a misfire just go away? ›

A misfire will not normally go away on its own. Instead, the damage compounds. And that damage can cost thousands to repair, if it is repairable at all.

What causes a misfire in cylinder 2 and 4? ›

The majority of the time, a misfire is caused by a faulty spark plug or another problem with the spark system, but it may also be due to: A fuel delivery problem. A mechanical engine failure. Exhaust gas recirculating.

Can a misfiring cylinder be fixed? ›

Usually, fixing a misfire is a pretty straightforward repair. However, there could be a deeper issue causing it, so it's always a good idea to have a professional mechanic look under your hood.

How do I find out what is causing my misfire? ›

To find the cause of a misfire, start with checking for trouble codes in the onboard diagnostics system with a scan tool. The codes may not pinpoint a specific part, but they should identify the cylinder or cylinders that are misfiring as well as other systems that aren't functioning properly.

References

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