What Causes An Engine To Backfire Through The Exhaust?

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Exhaust system leaks

There is nothing as loud, or as embarrassing, as hearing your car backfire as you drive down the street.

What causes your car to backfire and is it bad for your car? It is important to know where the backfire is occurring to know why it is happening and how you can fix it. Anytime your car is not right, it needs to be addressed before bigger damage can happen to your vehicle.

What Causes An Engine To Backfire Through The Exhaust
What Causes An Engine To Backfire Through The Exhaust

What is backfiring?

The very simple answer is that backfiring happens when the fuel combustion happens outside of the internal combustion chamber of your car. That is when you get that loud firing or popping noise.

What causes backfiring through the exhaust?

There are several reasons why your car maybe backfiring through the exhaust. Here are some of those reasons.

1. Faulty fuel injection system

If your car’s fuel injector is clogged or worn out, this will affect the air/fuel ratio. When this happens, not enough fuel is burned and left over in the engine. This leftover fuel then makes way into the exhaust. The leftover fuel in your vehicle’s exhaust then burns. That burning creates an “explosion”, giving you that loud sound.

2.Engine timing is off

The engine of your car is designed to run with precise timing. If that timing is off, you can have a problem.

If your car has delayed engine timing issues, this can cause the ignition cycle to start late. When this happens, the fuel is ignited while the exhaust valve is opening; instead of waiting for it to be fully opened.

3.Problems with spark plugs

Your car’s spark plugs could be causing your car to backfire. A worn out or damaged spark plug makes it difficult for the spark to jump or travel properly. This weakens the spark or even pushes it into a different area. The result is a loud backfire.

4.Engine Sensor Issues

Cars have a Mass Airflow Sensor. This sensor is responsible for calculating the amount of fuel to inject into the engine based on conditions. If this sensor is malfunctioning, it could send too little fuel. Once again, the fuel and air ratio is off, resulting in a backfire.

5.Exhaust system leaks

Another culprit is leaks with the exhaust system. If your car has leaks in the exhaust system, it is allowing more air to enter the exhaust system. This increase in oxygen cause the unburned or partially burned fuel to ignite. This causes that backfire noise that you hear.

Exhaust system leaks
Exhaust system leaks

6.Problems with the valve train

The valve train in your car is responsible for opening and closing the valves letting air and fuel into the combustion chamber.

If there are any valves that are not sealing correctly or not opening on time, you can have an issue. This can cause a buildup of carbon or other issues. Your car will backfire as well as possibly have other mechanical issues.

How can you figure out what is causing the backfire?

Since there are so many possibilities for backfire to happen, you need to pinpoint the problem in order to fix it.

If you have a bi-directional scanner, this is the perfect time to use it. You will need to plug this tool in underneath the steering column to get a diagnosis. The best obd2 scanner taps into your car’s onboard computer system to find errors.

Once it is done scanning your car’s computer, you will get an error code. Simply look up the code in the online manual for the scanner to see where the issue is originating from.

Do I have to fix my backfiring?

Yes. You need to figure out the reason and take steps to fix it. If your car is backfiring due to a leaking exhaust system or improperly closing valves, they need to be addressed. If not, your car could suffer more serious breakdown issues, as well as not pass inspection.

Can I fix the issue myself?

If you are handy with tools and comfortable under the hood, you can take a stab at fixing the issue. Use the scanner to give yourself a starting point.

It is relatively easy to clean and replace the Mass Airflow Sensor. Along with this sensor, you should check the air intake tube and make sure that is working properly. It connects the Mass Airflow Sensor to the throttle and then the engine.

You can also check the spark plugs. Replace them and make sure that everything is properly reconnected. You might also want to replace your car’s fuel filter. If debris has accumulated on the filter, it will affect the air and fuel ratio.

Checking for vacuum leaks is also something you can do if you are handy. You can use a smoke machine or carburetor cleaner to check for leaks and repair them.

Points to Remember

While your car backfiring does not mean you have to immediately stop driving it, it does mean that something is not quite right.

It is important to find out the cause of your car backfiring so that you can fix it. Cars backfire for many reasons. If you have a scanner you can use that to pin-point exactly where the problem is happening. If not, you may have to check several different areas.

Cars backfire when there is an excess of fuel that is being sparked somehow. It can happen if the valve timing is off, the spark plugs are bad or there are leaks in the exhaust system. It is important to find out and correct the issue.

Final Thoughts

Cars require routine maintenance. They also develop problems in between scheduled tune-ups. It is important that you take care of problems as soon as they crop up. A car that backfires is annoying. But it is also a sign that something is not working the way it should. Fix it yourself or take it to your professional so that you can be assured of a quiet ride once again.

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Mike Cross
Mike Cross
You have to look for teachers. If you want to be a mechanic, go hang out with mechanics.

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