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What Causes Engine Backfire (What to Do When You Experienced It)

Care my cars | Engine Backfire - Cause and What to do

Care my cars | Engine Backfire - Cause and What to do

Do you experienced engine backfire when you are cruising along a busy highway and hears a loud bang from your exhaust? That’s what usually happens to older cars where an explosion can occur in the air intake or the exhaust system instead of the combustion chamber. But what are really the causes of an engine backfiring?

 First of all, we need to determine if it is backfiring from the exhaust or just back up from the carburetor (also called carb by some mechanics). In automotive terms, an exhaust backfire is referred to as “backfiring” while backfiring from the carb are termed “coughing” or “spitting”. We will explain here some of the most well-known causes of engine backfire while you also learn more about “coughing”.

What is engine backfire?

engine backfire

Engine backfire - Via: Wikipedia

As we have stated above, engine backfire is a loud annoying sound that you may hear from the exhaust system which occurs mainly when you are accelerating. This could also happen even when your engine is in idle and you suddenly step on the gas for revving up. Automobile experts believed that backfiring is most likely to happen to older car models any time with several hundred thousands of mileage.

The backfiring through the carburetor (the coughing or spitting), on the other hand, frequently happens in the morning when the carb’s air/fuel mixture is too thin. However, this may not last long, a good one blast on that moment is all that it takes when the engine is totally warmed up. Additionally, the coughing may also be because of the accelerator pump of the carburetor not providing enough fuel prior to the main stream of gas gets working.

The carb might also be choked up or out of adjustment which is not impossible. Considering that as part of the fuel injection system, the carb is also subjected to stress, heat, and another form of tear and wear.

Here are some causes of backfiring engines

1. Rich fuel than normal

If the engine is being supplied with more fuel than air (also called running rich) which can’t be burnt efficiently, it may cause to backfire. Lack of sufficient air may be the result of blocked or dirty air filter. When an engine has too much fuel to burn with thin air, there could be a great possibility of creating incendiary fast-burning flame accompanied with a loud sound exiting the exhaust. Have your air filter cleaned or replace if necessary.

2. Bad ignition system

Your spark plugs may have something to do with bad ignition timing. This may entail cross firing which is the sending of spark to a cylinder with the intake valve open. Sometimes a plug or plugs spark out of turn enabling the fuel to burn prematurely in the cylinder and the product of combustion goes right to the open intake valve.

Then it goes right back via the intake manifold straight through the carb with a bang. You can have your spark plugs check for possible carbonation of the electrodes or a widening gap between the ground and center electrodes. You can check your spark plugs if they are still in good condition by using a spark plug tester if not, you may have to replace them.

Related post: Best Spark Plugs to Buy

3. External combustion

Another possible cause of backfiring is when your car’s internal combustion engine has a brief period of external combustion (or at least happening once other than the combustion cylinder). A small backfiring could also happen during deceleration due to a vehicle’s design especially modern cars offing for a sporting sound. However, when it is happening quite often and at an unexpected time, it is better to have your car check.

4. Bad air/fuel mix

Carbureted cars can really experience backfiring when there is an unbalanced air/fuel mixture. This could be adjusted manually by your mechanic. Traditionally, the ideal ratio is 14 part air to 1 part fuel (1:14 air/fuel ratio). However, for fuel-injected cars, the ratio could be adjusted through the car’s computer ECU for most modern cars.


An engine backfiring also has something to tell about the state of your car. This article will at least help you determine the causes of engine backfire so you may know what to do to fix it and save you some money repairing your car yourself. Although you may let your most trusted mechanic do the job if symptoms persist, you may be able to know what’s happening inside your car.

This could also be a wake-up call to have your car thoroughly maintained when its mileage is going further and further.

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