Last updated on August 1st, 2023 at 07:41 am
As a car owner, running into car troubles is only natural, and sometimes, it’s difficult to understand the problem with your car. Fortunately, most modern vehicles are outfitted with error detection systems that alert the driver of mechanical faults in the engine. It’s left for the driver to understand the code and take necessary actions. If your vehicle is showing the code P0304 on its OBD-11 scanner, it’s a critical sign that something is wrong with one of your vehicle’s cylinders, and it’s a case of misfiring.
This guide will explain what this error code means, its symptoms, possible causes, and what you can do about it.
Let’s delve right into it.
What is a P0304 Error Code and What Does it Mean for a Vehicle?
The P0304 error code is seen when the OBD scanner of the car detects a misfiring in one of the car’s cylinders, specifically cylinder 4. The job of the On-Board Diagnostic (OBD) scanner is to collect data and report any issues detected by the car’s Electronic Control Units (ECU). In doing so, if there’s any malfunctioning as detected by the ECU, the OBD scanner will promptly alert the driver with an error code. While the ECU keeps a tab on the functions of all cylinders, if anyone malfunctions by misfiring, it records the information and sends an alert to the scanner.
Why is this Important?
Your vehicle moves due to the power generated from its cylinders. Some vehicles feature 4, 6, 8, or 12-cylinder engines and so it doesn’t matter which type, provided the vehicle has at least 4 cylinders, a misfire of cylinder 4 is possible.
Now back to why these cylinders are important.
As earlier mentioned, they are responsible for the movement of your vehicle through the power they generate. Combustion occurs inside the cylinders to generate power. This happens when the fuel-air mixture inside the cylinders is compressed by the upward and downward movement of the pistons and ignited by a spark light which leads to combustion, and subsequent power generation that causes your wheels to move. The movement of the pistons occurs at specific times to compress and lead to combustion. If anything goes wrong with the timing of the pistons, the fuel-air mixture, or the spark, the whole system of power generation is messed up. Consequently, the check engine light reports it as a misfiring cylinder, with the number of the cylinder, which in this case is cylinder 4.
Causes of Cylinder 4 Misfiring
You will get the P0304 error code due to any of the following reasons.
- Wrong fuel-air mixture
- Faulty ignition system
- Faulty spark plugs (the most common cause)
- Dysfunctional fuel injector
- Leaking head gasket
- Poor compression from the engine
- Poor fuel pressure
- Leaking vacuum
- Substandard fuel
- Mechanical engine failure
Symptoms of a Misfiring Cylinder
While your OBD scanner can be trusted to detect a misfiring cylinder, faulty sensors can also trigger false alerts. It’s best to watch out for the signs yourself and know what to do. Here are clear symptoms of a misfiring cylinder.
- Poor engine performance
- Check engine is on
- Vigorous shaking of the engine while running
- Strange smells from the engine or exhaust
- Jerking during acceleration
- The check engine is blinking
How to Fix a Cylinder 4 Misfire?
When you’ve observed these symptoms or read the error code, the next action is to run a diagnosis. A proper diagnosis will reveal the cause of the misfiring cylinder, and it can be more than one. Diagnosing a misfiring cylinder is hardly a DIY job unless you have advanced mechanical knowledge and skills.
You will also need certain tools and equipment to run a thorough diagnosis, which may not be handy. Hence, calling your mechanic or auto technician is the right step.
However, there’s a high chance that a faulty or weak spark plug is the cause of the misfiring cylinder. You might want to change the spark plug first and observe the symptoms or check if the engine light is still on. You can watch the video below for how to replace your spark plug.
After changing the spark light plug and the symptoms persist, you can take the car to the mechanic.
Cylinder 4 Misfire Repair Costs
The price of repairing a misfiring cylinder varies depending on the cause, ranging from a worn-out spark plug to poor engine compression.
Running a thorough diagnosis to determine the cause also comes at a price and varies depending on the auto repair shop. Generally, running an hour of diagnosis can cost anywhere between $75 and $180, and it’s the labor spent in carrying out the diagnosis that you pay for, not the diagnosis itself. From the diagnosis, the auto repair shop can determine the price of fixing the problem and may incorporate the diagnostic cost into the overall price.
Generally, expect to spend between $66 and $250 for the least price of a minor issue like a faulty spark plug and $1500 to $2000 for a critical issue like a fuel injector.
How Serious is a Cylinder 4 Misfire?
A misfiring cylinder is enough to cause critical damage to your car’s engine if you fail to address the problem. Worse still, the problem can extend to other parts of the vehicle, such as its catalytic converter, which you know is very pricey.
Hence, always pay attention to the signs, and once you get an error code, stop using the vehicle until a proper diagnosis and subsequent repair is done.
Can You Drive With All Four Cylinders Misfiring?
One misfiring cylinder is enough to sign of potential damage to your engine, and all four cylinders misfiring is a recipe for engine disaster.
Though you may that it is impossible to drive your car when all four cylinders are misfiring thinking that the engine won’t generate enough power for motion I will that is that not the case. While it’s correct that driving a car with all cylinders misfiring would be highly difficult and inadvisable due to the risk of damaging the engine, it’s not necessarily “impossible. The engine might still run, albeit very poorly.
My recommendation is that when you notice any symptoms or the error code or misfires from your vehicle, quickly drive the car to the auto repair shop or call a mechanic. And if you are a DIYer, try to fix it yourself by identifying the cause which mostly will be due to a faulty spark plug, and replacing it that is the cause.
It should be treated urgently and not allowed to linger more than 36 hours.
How Long Can I Drive on a Misfiring Cylinder?
If your cylinder 4 is misfiring, how far you can drive that vehicle depends on its number of cylinders. For a V4 engine with 4 cylinders, one cylinder misfiring means your engine has lost 25% power generation and is functioning below par.
It’s also not impossible for the car to still drive around with 3 cylinders that can generate power, but very risky since you could lose engine power entirely if a second cylinder misfires.
The only reason you should drive with one cylinder misfiring is because you’re taking the vehicle to the nearest auto repair shop.
However, a V8 engine with 8 cylinders can still survive a couple of distances if one or two cylinders misfires. The other cylinders can compensate for it but will be under intense pressure to deliver power so that the overall engine performance will be diminished because of the misfiring cylinders.
Hi dear, my name is Jeffery Ekweghi, and I am a certified mechanic and autobody parts technician. I created this site to share my expertise and experience with car lovers looking to resolve their car-related issues. I am certified in private cars and heavy-duty commercial vehicles. I have worked as a mechanic since 2015 and have experience in vehicle brands like Subaru, Jeep, Toyota, TATA, BMW, Mazda, Honda, Nissan, Kia, TVs, and Others; however, I primarily specialize in Toyota vehicles.
