What Is Engine Misfiring? Can a Misfiring Engine Be Fixed?

We often write in our blogs about engine misfiring as a symptom of other problems. But what exactly does this mean?

In this article, we take a deeper dive into this phenomenon. Learn what happens when an engine misfires, what causes it, and the signs so you can recognize misfiring in your vehicle. We’ll also discuss the effects of engine misfire on your car’s components and whether engine misfiring can be repaired.

Volvo engine showing the cylinders where misfiring occurs
Image from Wikimedia Commons by OneAndOnlyLemonBird

What Is Engine Misfire?

When an engine misfires, a cylinder (or sometimes multiple cylinders) fails to produce power. Those cylinders in your engine are essential for the combustion reaction that powers your vehicle using a hydrocarbon fuel like gasoline or diesel.

In a gasoline-powered engine, the cylinder does not produce sufficient spark. In a diesel engine, you may recall that spark is not needed. Rather, high compression occurs to burn fuel. So during engine misfire, the cylinder in question doesn’t achieve enough compression for efficient combustion.

What Are the Causes of Engine Misfire?

Engine misfire can be caused by a multitude of problems, alone or in combination. It used to be that faulty spark plugs were one of the most common culprits. However, spark plugs are more durable and reliable these days, so there are other contributors.

When we see engine misfire, it’s often due to one of these issues:

  • Bad or clogged fuel injector resulting in only air in the combustion chamber
  • Malfunctioning ignition coil that creates combustion with the spark plug
  • Vacuum or hose leak that affects the amount of oxygen needed
  • Faulty emission system components, including the catalytic converter
  • Compromised seal, gasket, valve guide, or piston ring
  • Leaking or blown head gasket above the combustion chamber

Schematic showing how a catalytic converter works to clean vehicle emissions
Image from Wikimedia Commons by OpenStax

How to Tell If an Engine Is Misfiring

You may have experienced your vehicle’s engine misfiring and not even know it. Frequently, this will show up as the car stuttering or hesitating, particularly when you try to accelerate, and it feels like a sudden but transient loss of power. In some circumstances, the vehicle may stall.

You might also hear rattling or banging associated with a shuddering vibration under the hood. Sometimes people hear louder than normal noises from the exhaust, especially if that system’s parts are contributing to the problem.

Engine misfire can also occur when the vehicle is idling. Again, this typically presents as shaking or shuddering. If there is fuel or oil leaking where it shouldn’t go, with engine misfire, a burning smell is also noticeable. The “check engine” light may come on simultaneously with any of these signs.

Your mechanic could feel, hear, or smell these symptoms. Or they might run a diagnostic code test to see if the car or truck’s computer identifies a problem. This helps nail down diagnosis and eliminate guesswork so together you can decide on a plan of attack more quickly.

Most diagnostic code readers can identify which cylinder is at fault, in addition to other malfunctions that are related. You might even find the engine isn’t misfiring after all, and you actually have a problem with the brake pads or transmission.

Can Misfiring Damage an Engine?

There’s another sign of engine misfiring in some instances, and that’s poor fuel economy. But you shouldn’t be driving with a misfiring engine long enough to notice that one.

Why? Because engine misfire can be damaging to your engine. Leaking fluids can infiltrate parts and create a dirty engine. Worse, metal parts can become warped and need replacement or machining. If you keep driving with a cylinder leaving fuel unburned, it could permanently ruin your catalytic converter, even if the cat wasn’t originally involved in the misfire to begin with.

Newer vehicles today are finely tuned machines where each part relies on other parts functioning properly. It’s a bit like the human body. If one part fails, it can cause a cascade of problems elsewhere. With a car, truck, or van, letting engine misfiring go too long can result in much more expensive troubles down the line. Therefore, we always recommend seeing your mechanic as soon as possible if you suspect your engine is misfiring.

Can a Misfiring Engine Be Fixed?

Usually, an automobile engine that’s misfiring can be fixed, provided the owner doesn’t let the issue go on for too long. The engine repair will depend on what your mechanic finds once they look at the vehicle and evaluate what’s causing the misfire.

If there is damage resulting from ongoing misfiring, that will have to be repaired as well. Sometimes the engine will need to be cleaned up if fuel has accumulated outside the combustion area, for example. Or you could need a catalytic converter replacement. Each case is unique, and the sooner you get your vehicle into the shop, the sooner you’ll find a resolution to the engine misfiring problem.