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Summary
  • A misfire occurs when there’s incomplete (or zero) combustion taking place inside one of the engine’s cylinders.
  • The common causes of a cylinder misfire include ignition system problems, air-fuel mixture issues, and engine mechanical problems.
  • Aside from making your car unpleasant and unsafe to drive, a misfire can also cause additional damage to your vehicle.

A cylinder misfire is a common problem that can happen for a variety of reasons. When your car starts misfiring, you’ll likely notice engine performance problems, such as rough running and hesitation. The check engine light will usually illuminate, as well.

Not only does a misfire make your car unpleasant (and sometimes unsafe) to drive, but it can also cause additional damage to your vehicle. So, you’ll definitely want to diagnose and repair the problem right away. 

cylinder block of a car
An engine needs three primary ingredients to run properly: a precise air-fuel mixture, adequate spark, and good compression.

What is a Cylinder Misfire?

To understand a misfire, it helps to first have knowledge of how a gasoline engine creates energy by compressing and igniting an air-fuel mixture.

When the engine is running, a series of valves allow air (and fuel in the case of port injection) to enter each cylinder in sequence. After air and fuel have been pulled into one of the cylinders, the valves close and the piston moves upward in that cylinder to pressurize (compress) the mixture. 

Next, the spark plug fires and the air-fuel mixture is ignited. The explosion (combustion) forces the piston downward, causing the crankshaft to turn. The process is repeated in each of the engine’s cylinders to create the rotational force needed to propel your vehicle down the road.

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A misfire occurs when there’s incomplete (or zero) combustion taking place inside one of the engine’s cylinders. On a modern car, the problem will almost always trigger the check engine light. You might also notice that the engine runs rough, hesitates, or lacks power (or suffers from all three issues).  

What Causes a Cylinder Misfire? Common Causes

An engine needs three primary ingredients to run properly: a precise air-fuel mixture, adequate spark, and good compression. When one or more of these factors are missing, incomplete combustion occurs, resulting in a misfire. 

There are many potential engine misfire causes. Here are some of the most common: 

removing coil pack
A faulty coil pack can cause engine misfires.

Ignition System Problems

Ignition system problems that result in inadequate or improperly timed spark cause an engine misfire. Some examples include:

Air-fuel Mixture Issues

Any problem that throws off the engine’s air-fuel mixture can result in a misfire. Some examples include:

automotive fuel injectors
Bad or dirty fuel injectors can also lead to cylinder misfires.

Engine Mechanical Problems 

A variety of engine mechanical problems can result in a loss of compression, causing a misfire. Some examples include:

Sensor and Module Issues

Your car’s engine computer, which is often referred to as the powertrain control module (PCM), receives input from a wide range of sensors. The module then uses that information when deciding how to operate output devices, such as the ignition coils and fuel injectors. 

See also  How to Replace a Faulty Crankshaft Position Sensor

Many of the sensors the PCM relies on can cause a misfire when they fail. The module itself can also cause a misfire if it has an internal failure, such as a bad coil or injector driver. Some examples of sensor and module issues include:

mechanic holding maf sensor
Always check if your engine sensors are working well to avoid engine misfires.

Other Systems Failures

But wait—that’s not all. Modern vehicles are fitted with other engine-related equipment that can lead to a misfire when it fails. Some examples include:

  • Exhaust gas recirculation (EGR) system problems
  • Cylinder deactivation system problems
  • Variable valve timing system problems
  • Secondary air injection (SAI) system problems

FAQ

How long can you drive with a misfire?

A misfire can eventually damage the catalytic converter and possibly even the engine itself. As such, you’ll want to diagnose and repair the problem right away.

How do you diagnose a misfire?

Diagnosing a misfire can be difficult, especially if the problem is occurring on more than one cylinder. If you’re not particularly confident in your troubleshooting skills, you might want to leave the job to a professional. Otherwise, you can check out the videos below for an idea of what the diagnostic process might involve:

Other Notes About Cylinder Misfire

There are several related OBD-II codes to the cylinder misfire:

See also  P0300 Code: Random or Multiple Cylinder Misfire Detected

Get High-Quality Engine Parts For Your Vehicle 

You shouldn’t ignore engine problems like cylinder misfires because they can cause issues that can make your vehicle undrivable. Moreover, misfires can cause more engine damage, which can get expensive to repair. Good thing you don’t have to delay your repair since getting parts here at CarParts.com is quick and easy. 

CarParts.com is a trusted source of high-quality and affordable aftermarket parts. Our engine components like head gaskets, pistons, and timing belts are sourced from only the leading aftermarket brands. You can easily browse through our catalog using our vehicle selector and search filters. Order by 12 p.m ET., and you can expect your new part to get to your doorstep in as fast as two business days.

Don’t wait until some engine components break before replacing them. Check out our selection of engine components like head gaskets, pistons, and timing belts and shop today!

About The Author
Written By Automotive Subject Matter Expert at CarParts.com

Mia Bevacqua has over 14 years of experience in the auto industry and holds a bachelor’s degree in Advanced Automotive Systems. Certifications include ASE Master Automobile Technician, Master Medium/Heavy Truck Technician, L1, L2, L3, and L4 Advanced Level Specialist. Mia loves fixer-upper oddballs, like her 1987 Cavalier Z-24 and 1998 Astro Van AWD.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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