What Causes Backfire Through Exhaust – 5 Possible Reasons

Have you seen an old car that produces an annoying screeching sound as it stops on red light and fire likes a shotgun when its time to go? What is even worse is that it releases blue-black smoke from its tailpipe the covers the entire street.

We are not exaggerating on how a backfire occurs, but it is not inaccurate as well. The smoke is an indication that your engine is performing poorly. The screeching sound means that it is out of tune. And the outcome is usual in this situation. 


What Causes Car Backfire?

When the spark plugs ignite the fuel inside their cylinders, backfiring takes place. The exhaust valve opens on the barrel, and there is a delayed detonation of the combustion process. It produces the loud sound and makes the car jerk. Here are some reasons why backfire occurs

1. Running Too Rich

If more fuel is supplied to the engine more than it requires to burn efficiently, it is known as an abundant fuel to air mixture. There are lots of reasons that cause this including a dirty air filter.

If an engine is too affluent, there is lots of fuel that might cause an explosion, fast-burning flame. If that happens, the fuel combustion is not complete before the exhaust part of the engine cycle.

If on the cylinder the exhaust valve open, the extra air lets the unburned fuel to burn explosively, and you will hear the loud noise of a backfire. 

2. Bad Engine Timing

Incorrect timing can cause a backfire referred to as retarded timing. It means that the fuel-compression-ignition-exhaust engine cycle in the upper end (cylinder head) is not in coordination with the bottom end (cylinder block). It will cause the ignition cycle to start late in the combustion chamber and burn the fuel as the exhaust valve opens.

3. Broken Distributor Cap

In cars where spark plugs do not have ignition coils, a wire set, and a distributor cap are utilized to distribute the electrical pulse to the spark plugs. The one that causes the spark plug is the electrical pulse and ignite the fuel in its cylinder. The moisture might get in the broken distributor cap which can create a spark from the barrel to track to another, incorrect tube. A backfire takes place if the wrong cylinder fires out when the engine valve is open.

If your car has a distributor cap, replaced it every tune-up as part of your regular preventive maintenance. 

4. Carbon Tracking on Spark Plug Wires

Carbon tracking may occur in different scenarios. In a design that includes a distributor cap, connected to the top of the lid are all the spark plugs wire. As the time pass by, the environmental components may trigger the spark to cross over from one spark plug wire to those near to it.

If this thing frequently occurs a carbon track forms, it is a shortcut for the spark. It leads to misfire just like a cracked distributor cap.

Carbon tracking is also visible on ignition coils or sparks plug wires or ignition coils installed directly on the spark plug. Also, part of the spark takes the wrong path, and the rest is not enough to burn the fuel, which leaves some in the cylinder.

The next ignition can fire the spark plug, but it will require more fuel in the cylinder. This time it will not burn completely and as explosively as before the exhaust valve opens. The fast burn that may take place as the exhaust valve is open might result to backfire. 


Malfunctioning or Worn Air Gulp Valve

Cars manufactured in early 2000 may have an air injection unit that feeds into your exhaust system every time the engine is under load. It is needed to burn excess fuel, to result in an improved emission system. You will find an air gulp valve in the air injection system.

The valve lets the air enter the system if the engine is under load. If the gulp valve is malfunctioning, it releases air in the combustion system even during the de-acceleration which lead to a backfire due to the ignition of the unused fuel.

Note: The number of air gulp valve will depend on your manifolds. If your vehicle has one manifold, then you have one air gulp valve. If it has two, then you have two pipes.

The majority of the backfire incidents will have other signs connected to them like check engine light illuminated. If your car experience backfires, it is an indication that your vehicle is not working correctly and needs immediate attention.

It may not be a severe problem for you, but it is a sign of an impending issue or a precursor to a more serious concern.

Troubleshooting Backfire

Here are five easy steps to troubleshoots the backfire. It will not be discussed in this post thoroughly, but to give you an idea the troubleshooting will involve the parts that cause backfire. 


Final Words

To save you from the high cost of car repairs it is best that you do a regular servicing and proper maintenance to ensure that your vehicle is operating correctly. This guide is written to help you understand your car better and always to keep it in better shape. You need to address to any sign of malfunctioning in your vehicle to prevent further damage.

The engine and the other parts of your car function together thus a problem on one part might affect the others. Make sure to address it right away and appropriately.

If you find this guide helpful to you, feel free to share it with others. For inquiries and questions, you can comment below so we can address it right away. 

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