Why Does An Engine Backfire? 5 Most Common Reasons 

When a car engine backfires, it creates a loud sound and flames from the exhaust. They signal that there will be a big problem with your engine’s combustion. 

You can only address this issue by identifying the causes. So why does an engine backfire? Let’s follow us to find out the truth! 

Why Does An Engine Backfire?

Why Does An Engine Backfire

Bad timing, fuel mixture, old engine, deformed valves, and exhaust leaks are the most common causes of backfires. It’s necessary to check for these four elements to determine the right source of your problem. 

Bad timing

When combustion occurs outside of the engine’s combustion chambers, an engine backfire follows.

There is a perfect mixture of air and fuel in each cylinder. It powers your vehicle by igniting the mixture, resulting in explosions.

If the spark happens too late, unburnt air and fuel will pass through the exhaust. 

When the extremely hot fuel leaves the engine, it interacts with the surrounding air’s highly combustible oxygen. 

As a result, the unburned gasoline gets burned in the exhaust system instead of the engine. The combustion produces a loud bang and flames from the exhaust nozzle.

Fuel mixture

The spark within the chamber could not entirely burn up the gasoline if the engine has too much fuel while lacking air. A backfire might result from a little excess fuel vapor entering the exhaust.

The excess fuel amount in the engine can be the result of a broken airflow sensor or a blocked air filter. You may also blame the leaking fuel injectors. 

The same problem arises when there is too much air in the cylinder. Without enough fuel, the spark can’t ignite. 

Old engine 

Engines with older technology are more likely to backfire. Without a computerized system, they require continuous upgrades, sometimes known as tune-ups.

For instance, spark plug wires are no longer available in current vehicles. Instead, they have coil-on-plug configurations, which enhance the reliability and control of the engine’s spark-firing.

In an older car, the wires of a spark plug may get twisted or attached incorrectly, causing a spark in the cylinder. The spark will lead to a backfire. 

Deformed valves

Your automobile’s exhaust and intake valves control the flow of air into and out of the cylinders.

As a result, the intake valve allows air and fuel to enter the cylinder, where they ignite. Meanwhile, the exhaust valves expel fumes after the combustion. 

The combustion process malfunctions if any of the valves have faults, which causes your automobile to backfire. 

Exhaust leaks 

Your vehicle’s exhaust system allows more air into the system if there are leaks in it. Because of the surge in oxygen, unburned or partially burnt fuel will ignite. You can notice a backfire as a result. 

What Is The Difference Between Misfire And Backfire? 

A misfire occurs when a combustion process in the cylinder doesn’t complete. A cylinder doesn’t generate power when it misfires.

A misfire in a car will cause shaking or reluctance in the driver. The engine may severely vibrate as it misfires.

This video will give you more information about misfires:

Here are some differences between a misfire and a backfire:

Misfire Backfire
Cause  Cylinders can’t ignite the engine.  There is too much air or fuel for a smooth combustion.
Signs  Your car vibrates aggressively when accelerating and doesn’t run smoothly.  There is a popping sound and flames coming from the combustion. 
Damage  The car engine will degrade over time.   There will be power loss due to fuel efficiency, harming the engine power.
Solution Remove and replace the malfunctioning spark plug.   Change the oxygen sensors and cease air leaks. 

What Is A Backfire A Symptom Of? 

Your car backfiring is the first indication that it requires maintenance and repairs. 

A single backfire doesn’t damage the engine of your car. However, frequent backfires can destroy your exhaust system, particularly your catalytic converters, which are pricey to fix. 

Moreover, overlooking the source will worsen backfires. Your vehicle can reach “limp mode,” which lowers power to protect against drivetrain damage.

If you have a scanner, use it to detect the problem source. Otherwise, we advise getting your engine serviced. Professionals will tell you what is happening to your automobile and fix it correctly. 


With an excess of gasoline ignited in any way, your car might backfire.

The reasons can be incorrect engine timing, an unbalanced fuel mixture, an old engine, exhaust leaks, or deformed valves. Once you find out the reason, repair it as soon as possible to avoid further damage to your engine. 

Hopefully, you will find this guide helpful. For any further information, please feel free to ask. Thank you for reading! 

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