Why Is My Engine Misfiring?

Why Is My Engine Misfiring?

Why Is My Engine Misfiring?

When the combustion malfunctions, the engine misfires. Let’s find out the symptoms and causes of an engine misfire.

Modern or more recent engines tend to misfire more frequently. If you think your engine is misfiring, finding the source of the problem is typically difficult if you don’t know where to check or what to search for.

We shall discuss several potential causes of the issue with the aid of our guide. To begin with, you should be aware of the warning indicators to look out for.

Rough acceleration or rough idle are the two most typical indications that your engine is misfiring. Poor engine performance and the “check engine” light are other indicators. When an engine is misfiring, you may occasionally notice the check engine light blinking.

Symptoms of An Engine Misfire

The most typical indications or symptoms of an engine misfire are listed in detail below:

1. Rough acceleration

As we briefly mentioned. You may feel a strong or little jerking from the engine. Misfiring frequently occurs when the engine is under load, such as when you are speeding quickly. The most frequent causes of misfiring are high gear, low RPM, or a floored accelerator. The term “rough acceleration” describes this.

2. Rough idle

When the engine is idle, the engine sensors occasionally acquire incorrect readings, which causes the air-fuel mixture to be off. These problems can cause the idle to be very uneven, hop up and down, and otherwise be very unpleasant. In certain situations, the engine may even completely shut down.

The first location you should usually check into is the little air-fuel mixture issues that occur while your engine is idling because that is when your engine is most vulnerable.

3. Motions

Although the engine and axles of your car are often balanced during construction, there are certain methods to obtain the least amount of vibration.

The engine will become imbalanced if one or more of the cylinders are not firing properly. When accelerating or idling, this may cause loud vibrations inside the cabin.

4. Check the engine light

Why Is My Engine Misfiring?

The various engine sensors on more recent autos are well monitored by outstanding electronics. A sensor will tell the engine control unit if it malfunctions or detects a signal indicating anything is wrong with the engine.

The engine control unit will determine if the issue is serious or not after receiving the data. The engine control unit will illuminate the check engine light to alert you that something is wrong if the issue recurs multiple times. When that happens, it’s time to have it looked at and fixed.

5. Gradual acceleration

Misfiring might result in the O2 sensors receiving false information and producing a mixture that is either too rich or too thin. A rich or thin mixture can reduce acceleration, making your automobile appear underpowered. Your car won’t be able to rev over 3500 RPMs and could turn off the turbocharger’s boost pressure.

6. A modification to the engine’s sound

Even if you don’t know much about vehicles, you’ve probably noticed that different engines sound different from one another. A four-cylinder engine’s sound is very different from that of a V8 engine.

It may sound like a three-cylinder engine if a four-cylinder engine is misfiring on one cylinder. If the sound is unusual, it is probably misfiring on every cycle that may go wrong.

The Most Regular Causes of Engine Misfiring

A faulty ignition coil or spark plug is the primary cause of a car misfiring. A faulty fuel injector or fuel pump could be one of the main issues with fuel. It might, in extremely rare circumstances, be a low engine compression.

The most frequent causes of engine misfiring are listed below, starting with the most frequent cause:

1. A defective ignition coil or distributor in older vehicles

The ignition coil is typically the most problematic component. For each spark plug, some cars have a separate ignition coil, while others have a single coil with a sparking cable.

Older cars typically have an ignition coil and a distributor. Unplug each coil and search for any unresponsive cylinders if your spark plugs are separated.

Replace any damaged ignition coils or store a fault code specific to one ignition coil if you discover one.

2. A faulty spark plug

This ranks as the second most common reason for misfiring. The cylinders are ignited by the spark plugs, which over time may become worn out. Spark plugs are often inexpensive and simple to replace.

3. Leaks in the intake manifold gasket

When it comes to spark plugs, intake leaks close to the cylinder heads are rather typical. Older cars without intake steel gaskets had a lot more trouble with this specific issue.

You should look for leaks if your vehicle is older. If your automobile is more recent, it may be worthwhile to look for more leaks near the intake manifold gasket or the intake. Additionally, look for any broken vacuum hoses.

4. Reduced fuel pressure

A bad fuel pressure regulator, a bad fuel pump, or a blocked fuel filter could all be to blame for low fuel pressure. Low fuel pressure can cause a weak mixture in your engine, which can cause all of your cylinders to misfire.

You should absolutely check your fuel pressure if you receive issue codes for misfires on all of your cylinders.

5. Injector problems

A problem with this arose around 2017. Your engine may misfire due to a faulty fuel injector, which can be challenging to identify without flow testing.

Injector problems are less frequent in modern vehicles. Prior to checking the injector, make sure no other problems are present.

6. Low compression or internal engine damage

Even if you have done everything possible to rule out damage, your engine may still have low compression.

Low compression, which results in misfiring, could be brought on by a flawed timing belt adjustment. If you are aware that the timing belt has recently been changed, you should confirm with the installer.

7. The incorrect air-fuel ratio

Misfiring may result from an improper air-fuel combination. Your car’s sensors, including the MAF sensor, O2 sensor, coolant temperature sensor, and others, can all contribute to poor air-fuel mixtures.

Why Do Misfires Occur?

The fundamentals of an automobile engine must first be understood in order to comprehend what a misfire is. To make sure your pistons and crankshaft are moving inside the cylinder when your engine is operating, you need to take a good picture of them. The explosion inside the cylinder forces the pistons downward.

The piston is forced down by the rotating crankshaft. Because the engine operates in four phases, it is known as a four-stroke engine.

The process is as follows:

The explosion forces the piston downward while spinning the crankshaft as it descends, filling the cylinder with an air-fuel combination. The burned air-fuel mixture is expelled into the exhaust pipe when the piston rises once more.

That is how a four-stroke engine, which is present in nearly all contemporary automobile engines today, operates.

When one or more of these stages are incorrect or absent, a misfire occurs.

  • A dense or thin fuel/air combination
  • Incorrect ignition spark timing or a poor ignition spark
  • Low compression or a leak in the air-fuel combination
  • The air-fuel mixture’s inlet/outlet timing is improper.

Finding the person responsible for a misfire is much simpler now that you are aware of everything. Theoretically, there aren’t many factors that could lead to misfiring.

When you begin diagnosing your car, you will realize that it is not always as simple as you might believe to locate the issue.


Your ability to quickly solve the issue depends on your knowledge of how your car’s parts and devices operate. In order to prevent the problem from getting worse if you are not mechanically inclined or minded, call your specialist to have misfire issues inspected, rectified, or replaced.