An engine misfire occurs when, for one reason or another, the combustion process fails to execute properly and leaves the cylinders unfired, causing the engine to momentarily pause or stumble. Engine misfires usually mean something is wrong with the engine, and repeated misfires can seriously damage your vehicle’s internal components.

Experiencing an engine misfire can be startling and unexpected, but it’s something you should learn to recognize, as it may indicate something is out of sorts with your engine. Knowing what an engine misfire sounds and feels like—as well as what to do about it—can help prevent costly repairs.

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What is an engine misfire?

An engine misfire refers to the phenomenon when the internal combustion process momentarily falters, which causes the cylinders to go unfired. Once this happens, there is an extremely brief but noticeable loss of engine power, during which engine activity will pause or stumble.

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Loud engine noise

What does a misfire sound like?

When an engine misfires, it makes a very distinct sound, which you’ll be able to hear from inside the vehicle, and is most commonly described as a loud popping or chuffing sound. This sound is produced when unburnt fuel exits the cylinder out into the exhaust stroke, after which it is ignited by the next cylinder’s spark and explodes in the exhaust system.

An engine misfire or failing cylinder will make it sound as though your engine is struggling or wheezing, either while idling, accelerating, or both.

What does a misfire feel like?

If you experience a misfire while driving—and especially when accelerating—you’ll likely be able to feel it as it happens, depending on the cause of the misfire. If the issue is a faulty

oxygen sensor

, you may feel a slight hesitation while accelerating, or acceleration may feel rough. If the problem is a misfiring cylinder, you may feel the car shake as it unbalances the engine. Either way, a misfire will cause the vehicle to jerk slightly as the engine momentarily loses power.

If your vehicle misfires while idling—either shortly after starting the vehicle or while at a stoplight—it will feel as though the engine is struggling to keep the car running.

Key Takeaway If your engine’s internal combustion process is momentarily interrupted and misfires, you’ll be able to hear and feel it when it happens, regardless of whether you’re idling or actively driving.

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What causes an engine to misfire?

Your engine may misfire for a variety of reasons—there are a lot of engine components, after all—but most generally fit into one of three categories: fuel, spark, or mechanical misfires.

Fuel misfires: A dirty fuel cylinder, fuel injector, or clogged

fuel filter

can block fuel from reaching the cylinder, leading to a misfire—these happen most often while the vehicle is idling

Spark misfires: A spark misfire occurs when the

spark plugs

fail to ignite the fuel mixture, momentarily interrupting the combustion process—this can be due to a fouled plug or an issue with the wiring

Mechanical misfires: Out of all three, mechanical misfires are the most insidious and will only worsen over time, causing further damage to your engine—common causes are a damaged valvetrain, worn coils, leaking head gaskets, worn vacuum lines, damaged catalytic converter, defective oxygen sensor, etc.

Symptoms of a misfire

If you think you may have experienced an engine misfire, but aren’t entirely sure, look out for these associated symptoms:

Change in overall engine sounds

Rough or clunky idling

Black exhaust

Slow acceleration

Illumination of the

Check Engine light

What to do after your engine misfires

If you experience an engine misfire, the first thing you should do is schedule an appointment with your local auto repair shop so they can inspect your engine. Even if it only happens once, an engine misfire is often indicative of a larger issue with your vehicle. Visiting a mechanic right away can potentially save you from paying for more costly repairs down the line.

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FAQs

Why did my engine misfire?

At a base level, your engine misfired because—for some reason—the internal combustion process failed to execute properly, causing the cylinders to go unfired and leading to a momentary lapse in engine activity. An engine may misfire for many reasons, including a damaged spark plug, clogged fuel filter, defective O2 sensor, leaking head gaskets, and more.

Can I still drive after my engine misfires?

While it is still possible to drive after your engine misfires, it isn’t something you should ignore, and you should visit your local mechanic as soon as it is convenient to do so, so that they may inspect your engine.

An engine misfire may not seem like a big deal as it doesn’t prevent you from driving, but it often signals that something else may be wrong with your vehicle.

How much does it cost to fix an engine misfire?

Unfortunately, there is no clearly defined cost to repair an engine misfire, as there are so many reasons why an engine may misfire in the first place. If the culprit is something like bad spark plug wires, you may only have to pay $100 to get it fixed—but if the issue is with, say, the piston rings, you could be paying $3,000 for repairs.

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