Why Do Cars Backfire?

Why Do Cars Backfire?

No doubt, owning a car is a good thing. However, you need to understand that this can also come with several different issues, especially if you don’t perform complete routine service and maintenance on the vehicle. As a car owner, one of the many issues that you can experience with your vehicle is backfire.

A car backfiring brings a couple of sounds, such as a mild popping noise or a throaty gurgle. Sometimes, the sound could also come in the form of a loud noise coming from under the hood of your car. That’s not all; in some cases of car backfires, you can also see flames from the exhaust.

If you’re currently experiencing this issue, I’m sure you would have asked yourself this question – why do cars backfire?

It’s pretty simple; car backfires can occur when combustion, a result of the air-fuel mixture in the car, occurs somewhere outside the engine’s cylinders. A car can backfire if the timing of the internal combustion engine is bad. Lean fuel and rich fuel mixture are other common causes of backfires in your vehicle.

How exactly does a car engine work? What are the common causes of backfiring in vehicles? You’ll find answers to this question and a couple of others as you read through the rest of this post.

How Does a Car Engine Work?

Why Do Cars Backfire?

For you to fully understand what car backfiring means and what causes it, it’s important to first understand how car engines work.

So, here’s a quick question, how exactly do car engines work?

Combustion or burning is a high-temperature exothermic redox reaction that occurs between a fuel and an oxidant. In an internal combustion engine, that’s exactly what happens – the oxidant is usually atmospheric oxygen or air. The internal combustion system often takes advantage of this process to power your car. However, if the system fails to perform exactly how it should, car backfires are one of the things that occur. 

Here’s how the engine works:

  • It all starts with the intake valve opening up to draw in a mixture of fuel and air into the engine.
  • After that, the intake valve closes, allowing the piston to perform its function, which is to compress the fuel-air mixture.
  • Combustion will happen after the piston has successfully compressed the mixture. Here’s how it happens; a spark plug will go ahead and fire electricity to the air-fuel mixture, igniting it and causing combustion.
  • After combustion, what will happen next is a power stroke, a situation where the piston is pushed back by the gas coming from the combustion reaction.
  • Lastly, the exhaust valve will open and close from time to time, allowing smoke and other residues from the reaction of fuel and air to go out through the tailpipe of your vehicle.

That’s all about how the internal combustion engine works. Now, let’s go back and address the burning question of what car backfiring means.

What Does It Mean When a Car Backfires?

As you already know, the combustion process occurs inside the engine itself. However, if the ignition and combustion processes occur outside the engine (which is not supposed to be so), then what you’ll get is car backfiring.

As earlier mentioned, you’ll surely know when your car is backfiring. It often comes with a couple of sounds, such as a mild popping noise or a throaty gurgle. Furthermore, there are times when the issue could come in the form of a loud popping noise coming from under the hood of your car. That’s not all; you need to also understand that your car could also bring out flames from the exhaust if it’s backfiring.

This brings us to the next question of what causes cars to backfires. Find out in the next section of this post.

Why Do Cars Backfire?

Why Do Cars Backfire?

As you now know, a car backfiring happens when combustion and ignition, as a result of the air-fuel mixture, occurs somewhere outside the internal combustion engine.

But here’s a burning question, what causes combustion and ignition to occur outside the engine and not inside the engine itself? Several different factors can cause combustion and ignition to occur outside the engine. Let’s have a quick look at some of them below:

  • Poor fuel-air mixture

One of the factors that cause cars to backfire is when you have a poor fuel-air ratio. In this case, two different things are involved. The first one is when the mixture has too much fuel and too little air. The other case is when the mixture has too much air and too little fuel.

In a situation when the air-fuel mixture has too much fuel than air, you’ll have an engine that’s running rich. Unfortunately, this often slows down the combustion process inside the engine.

Since there’s a delay in the combustion process, the exhaust valve will open when there is an ongoing ignition of the air-fuel mixture. That’s exactly what causes “backfiring” or the combustion and ignition to occur outside the engine.

On the other hand, when the air in the air-fuel mixture is too much and the fuel is too little, the angle will start running lean. This will, unfortunately, also delay the combustion process, resulting in backfiring.

  • Bad engine timing

As previously mentioned, bad engine timing is another common cause of backfiring in a vehicle. A delayed timing occurs when the ignition process inside the engine fails to start on time. Backfiring occurs when the ignition cycle is still ongoing when the exhaust valve opens.

  • Bent valves

Now, you already know the function of the intake valve and the exhaust valve. In case you have an engine with bent valves, it’ll become pretty difficult for the valves to close properly.

For instance, the exhaust valve opens and closes to allow smoke and other residuals from the combination process to pass through the tailpipe. However, when the pipe has been, it means it’s not closing properly. This could cause the ignition cycle to occur outside the engine, resulting in backfiring.

Gui Hadlich

Hey there! I'm Gui. To be honest, I'm not really that interested in cars. But what I'm really, really not interest in is spending lots of money fixing my car up. Thankfully, I have a father-in-law who's obsessed with cars and a brother getting a PhD in internal combustion engines, so I get to learn about fixing cars. And with Fixing Engines, I hope to help you save a lot of money and take good care of your cars.

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