For your engine to work properly at all times, each cylinder must be firing correctly. If you’ve been having issues with cylinder 4 misfires, you may be wondering how much it will cost to fix the problem.
There are a number of things that can cause a cylinder 4 to misfire. Certain problems, like spark plugs or ignition coils, are relatively inexpensive to fix. Others, such as a valve adjustment or carbon build-up removal, are more costly.
Depending on the exact cause, it could be anywhere from $20 to $700 or more to fix a cylinder 4 misfire.
Below, we’ll discuss all the possible causes of a cylinder 4 misfire. Then, we’ll highlight the average price to resolve each of these problems.
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How Much Does It Cost to Fix a Cylinder 4 Misfire?
The cost to repair a cylinder 4 misfire depends on what exactly is causing the cylinder to misfire. Replacing the spark plugs is usually the cheapest fix, and removing carbon build-up is often the most expensive.
Since the repair cost can vary so widely, make sure you diagnose the issue correctly before purchasing any parts. The table below will highlight the average cost of repairing several common diagnoses.
| Diagnosis | Average DIY Repair Cost | Average Professional Repair Cost |
| Spark plug replacement | $20-$100 | $40-$150 |
| Ignition coil replacement | $50-$80 | $100-$200 |
| Distributor or wire replacement | $40-$60 | $90-$125 |
| Valve adjustment | $25-$70 | $250-$350 |
| Fuel injector replacement | $150-$600 | $350-$900 |
| Carbon build-up cleaning | Not recommended | $750-$1,200 |
These are some of the most common causes of a cylinder 4 misfire. Now, we’ll discuss what each one means and how you may be able to diagnose the problem.
What Causes a Cylinder 4 Misfire?
Any time your engine misfires, it means there’s something wrong with either your timing or ignition. Both of these systems are comprised of many components, so there are several things you might need to check.
Bad Spark Plugs
Your vehicle’s spark plugs are part of the ignition system. Spark plugs create the “spark” to ignite fuel in your engine, producing the power needed for it to run.
Spark plugs wear out fairly often, but thankfully, they’re simple and inexpensive to replace. Look in your owner’s manual to find where your spark plugs are located, then unbolt them to check for carbon build-up.
If the spark plug looks black from carbon build-up, it needs to be replaced. You might also notice that it’s covered in gas or oil. If so, it’s symptomatic of another issue.
If your spark plug is covered in gas, it means your vehicle is running rich. If it’s covered in oil, the valves or oil rings may be leaking inside the cylinder.
Before you take any other steps, replace the spark plug and see if the problem goes away. If the cylinder is still misfiring, you’ll need to check other components.
Bad Ignition Coils
Your ignition coils are what deliver power to your spark plugs. If one of your ignition coils goes bad, your check engine light will usually turn on. If it does, you can read the code and diagnose the problem this way.
If your check engine light does not turn on, you’ll have to troubleshoot the issue. To do this, try removing cylinder 4’s coil and replacing it with one from another cylinder. If this solves the problem, you’ll need to replace the ignition coil.
Bad Distributor or Wires
The distributor is an important part of the ignition system on older vehicles that use carburetors. Distributors use wires to send electricity to the spark plugs, and over time, these wires can corrode.
This will cause them to lose contact with the spark plugs, which then won’t get enough electricity to ignite fuel.
If the distributor or wires are not doing their job correctly, your engine will misfire. If you have an older vehicle with a distributor, check the wiring for any corrosion.
Unadjusted Valves
Your engine valves are responsible for letting air and fuel into and out of the cylinders. To do this, they must open and close at specific intervals. If they’re not doing so correctly, they’ll need to be adjusted to prevent misfires.
To adjust your valves, you’ll need to use a valve adjustment tool. These typically cost between $30-$80. However, it’s not easy to do and requires a lot of precision, so you might want to have a professional handle this task.
Bad Fuel Injectors
Your fuel injectors deliver fuel to the cylinders, which allow it to enter your engine and power your vehicle. If an injector isn’t working properly, however, the engine may misfire.
One reason fuel injectors stop working properly is clogging. Over time, these components can become clogged with so much debris that fuel cannot pass through. If this is the case, replacing the injector is the easiest solution.
Carbon Build-Up
While carbon build-up is often a symptom of a cylinder misfire, it can sometimes be the cause, as well. When misfires occur, the fuel inside the cylinder does not burn completely. This creates a lot of build-ups that can stick to both the valves and the piston.
If there’s significant carbon build-up in your engine, it can clog the exhaust valves. They will no longer seal properly, and as a result, you’ll experience misfires and a range of other issues.
Excessive carbon build-up will have to be removed professionally. The technician you visit will clean off the engine head, exhaust ports, and top of the piston, allowing your vehicle to run properly once again.
Symptoms of a Cylinder 4 Misfire
Most people have experienced a misfire while driving at some point. However, not everyone knows exactly how to detect them. Below, we’ll discuss a few of the symptoms associated with misfires so you know when they occur.
Shaking or Rough Running
One of the most obvious signs of a misfire is shaking or rough running. Your engine will start shaking if it cannot keep up with the momentum as you drive.
If you notice shaking or rough running while your vehicle is idle, it’s likely an ignition issue. It’s often due to the spark plugs, so this is one of the first things to check. If the spark plugs seem fine, check the ignition coils next.
An Unburnt Fuel Smell
If your exhaust fumes smell like unburnt fuel, or if you notice blue smoke coming from the exhaust, it may be a sign of a cylinder misfire. Both of these symptoms often mean that fuel is not igniting in a certain cylinder.
Jerking While Accelerating
If a cylinder isn’t functioning properly, your vehicle might jerk when you press on the gas. The engine isn’t working at its peak, so it may be having issues with acceleration.
This is often most noticeable on four-cylinder vehicles. Since there are fewer cylinders to divvy up the work, it’s more obvious when one of them is not working.
Increased Fuel Consumption
When your engine misfires, your O2 sensor receives inaccurate readings. It may think there’s not enough fuel inside of the engine, so the injectors will send more to the cylinders. This can also lead to your vehicle running richer, causing other problems if left unattended for too long.
The Check Engine Light Turns On
Sometimes, your vehicle will respond to misfires by illuminating the check engine light. You can read the code with an OBD2 scanner, a tool that costs around $30-$80.
If one of your cylinders is misfiring, your scanner will give you the code P0304. While it will not tell you which cylinder is having a problem, you may be able to tell by listening to the engine. If you’re still not sure, bring your vehicle to a mechanic so they can diagnose the misfiring cylinder.
Can You Drive with a Cylinder 4 Misfire?
Even if the problem does not seem severe, it’s never a good idea to drive with a misfiring cylinder. One of the most immediate dangers of doing so is a power loss and poor acceleration.
When you can’t accelerate well, you put yourself at risk if you need to act quickly. For example, you may need to speed up quickly to get out of the way of an oncoming vehicle. Poor acceleration may render this impossible.
In addition to these immediate dangers, driving with a misfiring engine increases the chance for further engine damage. Over time, misfires could damage your catalytic converter, pistons, or even your other cylinders. Eventually, your engine may stop working completely.
As a general rule, always get any misfires checked out as soon as possible. Continuing to drive while your engine is misfiring will almost always cause additional, more expensive problems.
Final Thoughts
Cylinder 4 misfires may be caused by a number of different issues. Some of these cost as little as $20 to fix, while others may be upwards of $700. Before you take any action, diagnose the issue correctly (or have a mechanic do so for you) so you know exactly what to repair.
