It’s something that most car owners have felt, and they get a pit in their stomach each time they do. The dreaded engine misfire. Misfires are notoriously difficult to diagnose, and most people dread them because they can lead to expensive repairs. In some cases, the misfire might happen once and never reappear. Other times, you might have to replace several parts before finally determining the root cause of the problem. We’re here to give you some of the most common causes of a misfire and tell you how to fix a misfire. So, if you’ve felt those sudden little losses of power in your engine, you’ll be prepared to handle it like a pro.
What Is An Engine Misfire?
Maybe your first question is, “What is a misfire?” Understanding a misfire first requires a basic understanding of how an internal combustion engine operates. Your engine requires air, fuel, and spark in order to run. Your fuel injectors spray fuel into the combustion chamber of your engine. At the same time, air enters this chamber through your intake valves. The piston travels upward, compressing this air / fuel mixture. Just as the piston reaches the top of its stroke, your ignition system causes the spark plug or ignition coil to fire. This ignites the fuel mixture and pushes the piston back down inside the cylinder.
Since your engine has multiple pistons and cylinders, they all work together in tandem moving up and down at different times. The pistons are connected to the crankshaft, so the crankshaft turns as the pistons move up and down. This turning of the crankshaft is what generates the power out of your engine and turns your transmission, hence making your car move.
Now, that is obviously a very high level view of your engine’s operation, but it gives you a general idea of how it operates. Now, let’s talk a little more about misfires. A misfire occurs when the fuel mixture in the combustion chamber of a given cylinder does not ignite properly or at the proper time.
Since this process is happening thousands of times per minute across anywhere from 4 to even 12 cylinders, then a single misfire does not typically cause your car to stop running. However, you can usually feel it when the miss occurs. Sometimes a misfire only occurs while idling and other times it might only occur under load. These misfires can occur for a number of reasons that we will explore, and they can sometimes happen just once or they might persist on a constant basis.
Most Common Causes Of Engine Misfires
Since you know that your engine firing requires air, fuel, and spark, you can also narrow down the list of potential causes for a misfire. It is almost always related to one of these three items. By following these guidelines, you should be able to step through each potential issue and narrow it down to find the specific cause.
In most cases, a misfire will cause your check engine light to illuminate on your dash, so you’ll probably need to reset your CEL once you correct the issue. At other times, you will even feel the misfire, especially if it is an ongoing issue that happens over and over again in the same cylinder. Either way, you’ll follow the same methods for determining the cause, although the singular, sporadic issue is often more difficult to track down.
1. Improperly Torqued Spark Plugs
The spark plugs provide the spark inside your cylinder that ignites the fuel mixture. If the spark is not present, then the ignition does not occur. Even if the spark is present, but is not strong enough, then the mixture in the combustion chamber will not ignite properly. Improperly torqued spark plugs may not fire correctly, thus causing a misfire in your engine.
If you replace the spark plugs in your vehicle, you should always use a torque wrench to make sure they are tightened to the appropriate spec per your manufacturer’s recommendation. Tightening them too tight can damage the electrode inside the plug and cause it not to fire. Similarly, keeping the plugs too loose can cause low compression and improper firing. Either issue is not good and may result in a misfire in your engine.
Many modern cars use ignition coils or coil packs instead of a single distributor that controls the spark. This allows the electrical signal to be delivered by the coil pack on each individual spark plug. This is a more efficient way of delivering the spark, and it can also help isolate spark issues because each cylinder essentially has its own ignition system. If your plugs are torqued to the proper specs, then you should also check for bad spark plugs or plug wires. If a spark plug is fouled out or the wires are bad, then the spark will not be delivered properly. You can try swapping coil packs from one cylinder to another and see if the misfire moves or stays where it is. This can confirm a bad coil pack.
2. Fuel Injectors
We’ve already talked about the spark component, so now let’s discuss the fuel. Your car’s fuel injectors spray the fuel into the combustion chamber. Your vehicle’s computer tells the fuel system exactly how much fuel should be sprayed. If too much or too little fuel is sprayed, then it will affect the engine’s firing.
Over time, fuel injectors begin to get dirty with carbon buildup and other contaminants. These devices work with very precise amounts of fuel as they spray a fine mist of fuel. Even a slight clog in the injector will cause too little fuel to be delivered. When this happens, the combustion that takes place will not be large enough, and a misfire will occur. As a car starts to get above 75,000 miles, this buildup is bound to happen. You should make sure that your injectors remain clean by using a cleaner additive in your fuel tank at least once every oil change.
In addition to your injectors, there are other fuel delivery problems that could be causing misfires. A clogged fuel filter or low fuel pressure from a bad fuel pump or faulty fuel pressure regulator could be the reason your vehicle is not getting enough fuel in the system. Believe it or not, too much fuel can cause misfires too. In addition, too much fuel can cause problems with your catalytic converter and failed emissions tests. If any of those problems are occurring, you should get them corrected right away as they can lead to poor fuel economy and even worse.
3. Ignition System
While your spark plugs provide the physical spark inside the cylinder, the ignition system is responsible for sending an electrical current to the plug and thus creating the actual spark. If your plugs are not receiving a signal, then they will not fire. They might also be receiving a signal, but at the wrong time. This spells trouble too, and both of those problems are related to your ignition system. Ignition system problems can even cause your car not to start or even cause you to get just a clicking noise when you turn the key.
In older cars, your ignition system was controlled by a manual distributor that fired based on the timing of the engine spinning. However, today’s cars have systems that are completely controlled by the car’s computer. It knows exactly when the signal should be sent to the spark plugs, and it sends that signal from the distributor cap through the spark plug wires to the plugs. Your timing belt helps keep all the mechanical parts like the valves and pistons in sync to the firing of the ignition system.
4. Air To Fuel Ratio Problems
You may have heard people discussing a car that was running too lean or too rich. This has to do with the air / fuel ratio inside the cylinder heads. If a vehicle is getting too little fuel, it is said to be running too lean and too much fuel leads to a mixture that is too rich. Either of these scenarios will cause a misfiring engine. A rich mixture can even cause your engine to backfire as well.
The cause of these problems could be related to your fuel system as mentioned above or even your mass airflow sensor or throttle body. If your engine is not getting the proper amount of air, then your ratio will be off even if your fuel system is working properly. A bad throttle position sensor can cause problems with your air / fuel ratio as well. Vacuum leaks are notorious for causing air to fuel ratio problems and misfires too. This could be due to a loose or cracked vacuum hose.
5. Loss Of Compression
This is a cause that you probably don’t want to hear. Loss of compression is a big deal, and it’s usually not a simple fix. When your car loses compression, it’s usually because you have a blown head gasket. You might notice that your coolant has started to mix with your oil or vice versa. If this is the cause of the misfire, then you better get out your wallet. Replacing an automotive head gasket is not an easy task, and it’s no cheap repair.
Head gaskets usually blow due to overheating or excessive pressure in the engine. When this happens, you’ve probably damaged other parts like piston rings and maybe even the pistons themselves. You’ll also want to check and make sure the intake manifold gasket is still in good shape while you’re there. You’ll likely notice an extreme loss of power along with this symptom too. Make sure you fix this problem soon or otherwise you’ll be paying for a complete engine rebuild.
How Much Does It Cost To Fix An Engine Misfire?
The cost to fix the misfire problem depends heavily on what the real problem is. You can start by having a mechanic use a scan tool to read the diagnostic trouble codes from your car’s computer. This code reader can pull the misfire code and provide a little more detail about the cause of the issue. Often, the misfire code is very generic. It might state “misfire in cylinder 3.” Thanks, but you probably already knew that. Other times, you might get lucky and have it provide more detail about what caused the problem.
Simple issues like bad spark plugs or dirty fuel injectors will only cost you a few hundred dollars. You might even be able to correct this problem yourself without the help of a mechanic if you are pretty handy with DIY tasks. However, if you have a loss of compression, then your repair bill is probably going to be much higher. Replacing a head gasket can cost $1,000 or more depending on your specific vehicle.
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You felt the dreaded misfire and your check engine light came on, so now what? You can use the information you learned here to help diagnose the cause of the problem and decide how to proceed. Some fixes are fairly simple, while others are much more involved and expensive. If yours falls on the expensive side, then you do have options. You could sell your car to Auto Wranglers for cash and buy yourself a new one. Contact us today to get your cash offer and get the process started!
Is it safe to continue driving with an engine misfire?
In most cases, it is perfectly safe to drive with a sporadic engine misfire. If the misfire is happening all the time, then you shouldn’t drive your vehicle until it’s fixed. With a constant misfire, your car will lose power and could possibly stall on you. That makes driving around too dangerous until the vehicle is fixed.
What does an engine misfire feel like?
A misfire feels like a sudden “miss” or your engine cutting out for a split second. You might feel a slight pulse each time the engine misfires, and you could even hear a backfire if the problem becomes extreme.
What is the difference between a misfire and a dead cylinder?
A cylinder misfire occurs when a single firing in the cylinder does not work properly. The other thousands of firings there are taking place normally. A dead cylinder means that one of your cylinders is not firing at all. A dead cylinder is a serious issue and leads to a noticeable loss of power in your engine and extremely rough running.
Can a misfire ruin an engine?
It is rare that an engine misfire causes any serious damage to your engine. Misfires are fairly common, especially in engines with high mileage. However, left unchecked, a misfire will begin to get worse and could result in a dead cylinder or cause more damage if not corrected.