Engine Misfiring: Symptoms & Causes (Explained)

A misfiring engine is a common experience for most drivers. However, very few drivers truly understand what a misfire is or what causes engine misfiring. This article seeks to explain misfiring and jerking in automobiles and the causes and symptoms associated with them.

What is engine misfiring?

Engine Misfire

Engine misfire occurs when there is incomplete combustion in the engine cylinder or when the combustion chamber is malfunctioning. You know there is an engine misfire when you accelerate your vehicle, and it responds with an unusual shaking sound. It indicates that the emission from the engine is abnormal.

For your engine to fire the cylinder, it depends on three main components: fuel to burn, oxygen to aid the burning reaction, and a spark to ignite the engine. In more modern cars, the dashboard will show a check engine light when there is a misfire.

Also, the car exhaust will give off a cloud of black smoke. It is a sign that the emission from the engine to the exhaust is not dense, and the exhaust will be making funny sounds. Engine misfire reduces the efficiency of the engine and consequently the speed of the car.

Causes of Engine misfiring

There are several reasons why a car engine misfires including a bad spark plug or ignition coil, nozzle, and also insufficient intake of fuel and air. Similarly, inactive compression, the presence of water in the fuel tank, and a problem with the car’s exhaust are common causes of engine misfiring.

Spark plug

Bad spark plug

A bad or clogged spark plug is the most common cause of engine misfiring. Misfiring occurs when the spark plug is not getting enough current from the coil.

Spark plugs are small metallic devices found in the engine of your car. They help your engine to convert gasoline which is in potential energy to kinetic energy.

In reality, spark plugs help your engine ignite the fuel/air mixture by an electric spark while containing the combustion pressure. We have a detailed article on spark plugs that explains their functions in-depth. Three elements make up the spark plug;

  • Ceramic base
  • Electron
  • Metallic base

If there is an issue with the coil and it blazes the ceramic base, there will be a short circuit leading to an engine misfire. The electrons that link the ceramic base to the metal base have a maximum gauge of 0.2m. When it sends current, and it does not ignite the other base quickly, it means the spark plug is faulty.

Checking the diameter of a spark plug

When the ceramic base has internal cracks, the current will not flow. It shows the plug at this point faulty. Similarly, if the engine ring is passing excess lubricant to the face of the plug, the plug will shut down.

How to identify Spark plug as the cause of Misfiring?

Spark plug as cause of misfire

Loose out the spark plug from the high gauge. At this point, you can see the surface of the plug and how the plug function. If there is no black carbon at the surface, it means your car plugs are burning well.Check your electrons if they are at the maximum. Then, the spark plug is okay. If the ceramic base is intact, it means there is no issue with the spark plug.

Other causes of engine misfiring

  • Nozzle

If the fuel pump is not transmitting enough fuel to the nozzle, the nozzle will not open. This fault will lead to an engine misfire.

  • Ignition Coil
Ignition Coil

Increased discharges and gas smell coming from the exhaust is a sign that the ignition coil is bad. A defective ignition coil can cause a vehicle to stop moving or misfire because of uneven sparks sent by the spark plugs due to the faulty coil. You can see our article on the ignition coil to understand this better.

  • Insufficient intake of fuel and air

When the intake of fuel and air is incomplete, it will cause the engine to misfire. This can either be a shortage of are due to clogged air filters, or insufficient fuel entering the combustion chamber.

  • Presence of water in the fuel tank

If there is water in the fuel tank, because of the high density of water, it will cause water to go down the combustion chamber while the gasoline remains on top. The volume of water is higher than that of gasoline. Once the water gets to the combustion chamber, it will lead to a misfire.

  • The exhaust

The exhaust system has some components which when impaired, can cause the engine to misfire. Some of them include a bad manifold gasket, a faulty muffler, a blocked catalytic converter. A bad exhaust manifold gasket can disrupt the air-fuel ratio and cause engine operation issues such as misfire. Check out some other symptoms of a bad exhaust manifold gasket.

If the muffler has a crack inside, it loses its efficiency and can result in misfiring in the engine. When the catalytic converter gets blocked, it constrains the exhaust flow, making less air get into the engine. Thus, this results in a misfiring engine. To better understand how the exhaust of an automobile works, we advise that you read our article on the Exhaust system.

  • When the compression is not active
Intake valves, exhaust valves, fluid filled chamber

When your engine rings are weak and do not produce the expected compression level from the bottom-dead-center, the operation will be hampered and lead to a misfire. A rare cause of engine misfire is the valve.

After checking the other causes of a misfire, the last unit to look at is the valve. To understand the role the valve plays in an engine misfire, you should read our article on valve timing. Valve timing is the mechanism that determines the precise time engine valves are to open and close.

What is car jerking, and what causes it?

Car jerking occurs when something interferes with the circulation and transmission of power in the engine. It is also a sign that your car can develop other problems if you don't check the engine in time.

Car jerking can result from the obstruction of fuel or airflow. Problems such as faulty spark plugs or wires, soiled fuel injectors, clogged air filters, dented cylinders, blocked catalytic converters, impaired gas lines, spoiled acceleration cables, faulty carburetors, and moisture on the distributor cap can also make your car jerk.

Why is my car jerking on acceleration?

If a car engine cylinder is not functioning well, the first take-off will lead to a misfire which causes the car to jerk. Car jerking hinders the smooth movement of a vehicle. For a manual car (if you’re an inexperienced driver), and your car jerks a lot, the problem might not be from your engine.

Rather your automobile may experience this jerking because you didn’t switch gears properly. Learning how to drive a manual car will resolve this in no time.

While for an automatic car, your vehicle can jerk for a lot of reasons. These reasons range from a bad spark plug to dirty fuel injectors to blocked a catalytic converter, etc.

Can bad gasoline cause car jerks?

Yes, if the fuel is not properly refined or water in the fuel can lead to your engine misfiring. Hence, you should avoid having water in your fuel tank and steer clear of bad fuel.

Is jerking the same as a misfiring engine?

Misfiring leads to car jerking. When a car misfires, it starts to jerk. What makes a car jerk and misfire are very similar, hence the terms are used interchangeably.

Can a misfire ruin an engine?

Yes, a misfire causes more force/load to be placed on the engine when you drive. It also causes more fuel intake, which can damage your engine.

We do not advise you to keep driving when your engine misfire. The longer you keep on using the vehicle, the more damage you will cause to the engine. Recurrent misfiring could cause some costly issues that could eventually end your engine.

Is engine misfire expensive to repair?

It is not expensive. The cost of repair in an engine when there is a misfire is relatively low. Also, the cost of fixing a misfiring engine depends on the cause of the misfire. There are several causes of a misfiring engine, and this will determine the cost of repair.

Can a misfire go away on its own?

Driving a car with a misfiring cylinder

You have to fix your car engine when it misfires. It doesn’t go away on its own. The only instance when a misfire corrects itself is when it starts early in the morning. When your car misfires in the morning, this misfire could be because of the kind of fuel in use.

The gasoline in use these days takes time to burn out. So when you start your vehicle in the morning, it is advised to let it steam for at least five minutes before accelerating. When the car starts, it may shake more than normal, but after it steams for some time, it burns off the impurities in the combustion chamber, causing the car to be stable.

Symptoms of a misfiring engine

  • The vibration of the engine affects the body of the car.
  • You will hear a shaking sound if you accelerate your car immediately after turning on your engine.
  • When driving, your engine will not function at its optimal speed.
  • The smoke from the exhaust will be very black.
  • When your car stops and starts suddenly.
  • Your check engine light will start flashing.

What to do when your engine misfires?

  • Take note of unusual sounds or behavior of your vehicle.
  • Watch how frequently the misfire occurs.
  • Drive your vehicle to a car technician and have it fixed.


Misfiring engines can occur due to several reasons. The most common reasons include a faulty spark plug or ignition coil, faulty nozzle, exhaust system problems, and water in the fuel tank. Lastly, the cause of misfiring should be carefully determined and fixed quickly to prevent it from damaging other components.

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