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What Causes a Car to Backfire: Important Things You Need to Know About The Engine

what causes a car to backfire

As a car owner, I’ve experienced so many instances where my car backfires. The degree of failing depends. It can be a quick backfire, or it can be continuous and loud, which may be a little scary.

After I’ve undergone a crash course in automotive technology, I learned the basics of the engine. Most notably, I learned how to troubleshoot and figure what causes a car to backfire? Stay tuned as we’ll talk about the most important things when it comes to failing!

Explaining the Engine

When your car backfires, it can be caused by so many factors. However, these factors are limited to one intricate component of your vehicle, and that’s the engine. Other parts like the differential, the transmission, and the chassis do not have any relationship to backfiring.

The engine of your car works in a very complicated manner. For one, it starts off with the combustion chamber that connects to different components. This portion is where all the combustion happens in your car, which is responsible for your vehicle’s mechanical movement.

The air-fuel combustion inside the chamber uses a systematic process to convert fuel into energy. It is called a stroke cycle, which can come in different orders and numbers.

To use an example, we’ll focus on the four-stroke cycle. It is easily the most typical process of an engine. You can commonly apply this to most cars and other vehicles like trucks.

The term four-stroke cycle comes from four stages of how the fuel transforms into an energy source that powers the engine. These four steps have a chronological arrangement of 1) intake, 2) compression, 3) combustion, 4) exhaust.

four stroke cycle

Photo Credit: pinterest.com

To further explain, let’s discuss each stage. The first step, which is the intake process, is when your engine allows the entry of fuel and air inside the combustion chamber. So how does this entry happen? Well, it happens to a pair of valves located in each cylinder.

The cylinder is the area where the pistons travel. The pistons, on the other hand, are the primary source of mechanical power that “pumps” the air-fuel mixture inside the combustion chamber.

Now, going back, each cylinder has two valves that serve as the entry and exit point of the fuel. Thus, the two valves in each cylinder have labels of intake and exhaust valve.

It is where it starts to get tricky. The intake valve naturally opens to allow the entry of the air-fuel mixture. Similarly, when the process is in the exhaust stroke, the exhaust valve is open. For every hit, there’s a correct combination of unfastened and closed valves on all cylinders.

More importantly, the timing of the valves on their opening and closing should be perfectly in-sync with the entire process of the engine. Now, should a valve or two be in the wrong valve timing, backfiring will occur.

The “popping” sound from a backfiring engine usually comes from the spark plug working with the engine. Spark plugs provide the electrical spark in the combustion chamber which ignites the air-fuel mixture. Because of the mistiming of the valves, the spark plugs ignite the mixture at wrong stages, causing the popping sound.

Read more: How to Fix Oil on Spark Plug Threads in 5 Easy Steps

Understanding Backfiring: Symptoms and Other Causes

Backfiring is used in automotive because the event literally “fails” against your engine. It means that the engine cannot provide any efficient means of combustion to allow the vehicle to move. That is why backfiring happens when you start the engine, but it fails to complete its process. Thus, leading to an immobile car.

Related: https://automotiveward.com/bad-starter-symptoms/

Now, all of us who have experienced backfiring will know that the number one sign of it is a stuttering and popping sound within the cylinders. Worst, some cases of backfiring has louder snapping sounds that also physically stresses out the engine itself.

You may trace other signs of backfiring in the exhaust pipe. A bluish black smoke emitting from the exhaust pipe is a chemical reaction that comes from the dysfunctionality of the valves.

black smoke exhaust

Photo: https://www.reference.com/

If ever your car does accelerate, it will still have symptoms later on. Some of the signs to look after is a car that’s lurching and jerking. The tires you’ll have will also screech once in awhile due to the uneven friction caused by the jerking vehicle. It sounds an awful experience!

Cracked Distributor Cap

As we previously mentioned, backfiring comes from a lot of problems in the car. The most common case is the mistiming of the valves, but there are other components in your vehicle to check.

One of these is the distributor cap. The distributor cap’s connection with backfiring is when the engine does not use an ignition coil for the spark plugs. Instead, you can use the cap and the wiring set to provide an electrical pulse towards the spark plugs.

Now, if a cracked distributor cap occurs inside the engine, this may cause moisture build up. The buildup of moisture can significantly affect how it can send the electrical shock. Notably, the ignition from the spark plug can inadvertently transfer to another cylinder that you should never attempt to ignite. Thus, causing the popping sound.

Rich Fuel-air Mixture

This problem particularly focuses on the oversupply of fuel. The balance of air and fuel is disrupted, with fuel being too generous. It causes backfiring in the engine’s combustion process.

Too much engine fuel will cause slower combustion and burning. That means that there will be excess fuel inside the chamber once the exhaust stroke happens. When the exhaust valve opens during the exhaust stroke, the extra fuel explodes. The explosion occurs because of the extra air entering the valve, causing an intense popping noise.

One of the main reasons for this is a faulty or dirty air filter. The air filter is responsible for cleaning the air before it reaches the carburettor of fuel injection system. These two components of the engine then mix air and fuel to create a balanced ration between the two.

Wrapping It Up

Backfiring is a common problem, especially with older vehicles. Although common, it can be a headache to do, which is why a lot of car owners get it inspected by a professional. However, you can troubleshoot a backfiring engine in under an hour.

That is the case as long as you follow specific instructions in handling the valves.

Still, the best case scenario is not to experience this at all. Proper maintenance and weekly inspection of the engine is a good start to your car’s overall health. Remember, prevention is the best cure, so always give your engine a lot of love!

Steven K. Galloway