How to fix an Engine Misfire – DIY

how to fix engine misfire

A misfiring engine can be an unpleasant experience. Not only does it make a loud popping sound accompanied by possible thick smoke, but it certainly signals there’s an issue – sometimes a serious one – with your car’s engine. In this article, we will explain how to fix an engine misfire by own.

how to fix engine misfire

For the safety of you and your passengers, along with the well-being of your vehicle, a misfiring engine is not something you want to put off fixing. In this article, we’ll explore some common reasons your car’s engine is misfiring, how to diagnose the cause of an engine misfire, and some DIY fixes to hopefully prevent you from having to purchase a remanufactured engine replacement.

How Does a Car Engine Work?

First, before we dive into some engine misfire causes, let’s explore how a car engine works.

Most internal-combustion engines operate in four steps, which are known as strokes, in regards to the four different strokes a piston makes to complete each cycle. In a four-stroke engine, the four strokes include intake, compression, power, and exhaust.

  1. Intake stroke. During this stroke, the piston moves in a downward motion to allow a mixture of air and fuel into the cylinder.
  2. Compression. This stroke starts at the end of the suction stroke. During this step, the piston compresses the air-fuel mixture.
  3. Combustion. This stage generates the engine’s power. During the combustion phase, the spark plug ignites the fuel-air mixture.
  4. Exhaust. This is the final stroke that occurs when the exhaust valve is open and the intake valve is closed. When the piston returns from the bottom dead center to the top dead center, the spent air-fuel mixture is released through the exhaust valve.

What Does an Engine Misfire Feel Like?

If you believe your engine is misfiring but aren’t exactly sure what the symptoms of engine misfiring are, look for some of these common engine misfire symptoms:

  • The engine is difficult to start
  • The engine loses all power
  • Emissions increase
  • The engine makes a popping sound
  • The engine stalls, jerks, or vibrates
  • The exhaust or intake manifold backfires
  • Your car’s fuel consumption rises

If you notice any of these signs, it’s important to take your vehicle to a trusted mechanic as soon as possible, as it’s not safe to operate a vehicle with a misfiring engine.

What Causes an Engine to Misfire

Here are a few of the most common reasons your car’s engine might be misfiring:

An Imbalance in the Air-to-Fuel Ratio

What causes an engine to misfire? An imbalance in the air-to-fuel ratio is one of the most common causes of an engine misfire. An imbalance in the ratio means there’s not enough fuel and too much air being mixed together. Without the right proportion of air and fuel entering your car’s engine, you’ll notice a misfire while you’re idling. Causes of this issue may include a clogged fuel filter, a bad fuel pump, bad or old gas, or a bad airflow sensor.

Ignition System

Ignition system problems can also cause a car engine to misfire. Misfires because of worn-out or improperly installed spark plugs were a common problem in older vehicles because spark plugs only lasted about 10,000 miles. Due to advancements in technology, modern spark plugs can now last 100,000 miles or more. However, spark plugs can still wear out over time and prevent them from firing at full strength.

Aside from the spark plugs not receiving adequate spark from the internal combustion chamber, you may also have a worn-out ignition cable, distributor cap, ignition coil, or rotor on your hands.

Mechanical Problems

Your car contains several parts that lead to the functionality of your engine, including the pistons, valves, cylinder walls, and camshaft rings. If one of these parts isn’t working properly, it can lead to an engine misfire. Some other possible causes of engine misfiring include damaged rocker arms or a back fuel injector.

Issues with the Fuel Injector

Fuel injectors are located in the intake manifold and are responsible for breaking up fuel into a fine spray. They can fail over time if they become clogged or dirty. When this occurs, and the fuel injector can’t deliver fuel, there’s only air in the combustion chamber, leading to an engine misfire.

Vacuum Leaks

Engines have vacuum hoses that help enable airflow. When one of the hoses develops a pinhole leak, the vehicle’s onboard computer can’t determine how much air and fuel are needed for the combustion chamber, which can eventually result in a misfire.

Catalytic Converter

A clogged catalytic converter can also be the culprit. When your car’s catalytic converter becomes clogged, it can create problems including overheating and misfiring.

Engine Control Module

A glitch in the engine control module can negatively impact the combustion process and cause an engine to misfire.

Transmission Issues

On rare occasions, a misfire may not come from your engine at all, but, instead, the transmission. If your car is jerking around while you’re driving, the transmission may not be able to shift up and down appropriately, making it feel like an engine misfire has just occurred. This is especially common while driving at high speeds.

How to Fix Engine Misfire

If you’re not handy working on cars, it’s best to take your vehicle to a mechanic so they can perform a full inspection and make the appropriate repair. But for more experienced DIY car owners, there are a few tricks you can perform at home to repair a misfiring car engine.

Carefully review your car’s owner’s manual when performing any work on car engines so you avoid causing more harm than good.

Spark Plugs

Fixing worn-out spark plugs is the easiest and cheapest fix for an engine that’s misfiring. They cost about $10 and can be found at any auto parts store. In order to achieve consistent performance, it’s best to replace all of the spark plugs at once. Spark plugs typically cost about $60 per set.

Spark Plug Wires

If you’re already changing the spark plugs, consider changing the spark plug wires at the same time since you have to remove the spark plug wires when you change out the plugs. Spark plug wires also wear out over time, so they will eventually need to be replaced anyway, usually around the same time the spark plugs need to be changed out. Spark plug wires run on average $30 to $80.

Ignition Coils

Ignition coils can commonly wear down due to worn-out spark plugs and spark plug wires. A failing coil to the ignition can lead to misfires and roughness while driving, which can eventually damage your car’s catalytic converter or engine computer. Depending on the age of your car, it may have one or more ignition coils.

If you decide to replace the ignition coils at home, practice safety and make sure to disconnect your batteries first. An ignition coil may run anywhere from $75 to $300 as part of the engine misfire cost.


For the safety of your and your passengers, as well as the health of your car’s engine, it’s important to have a misfiring engine inspected right away – either by a reputable auto mechanic or through the DIY methods we explained in this article. If you decide to fix the issue yourself, be sure to consult your owner’s manual to ensure you’re performing the repair correctly to prevent causing more harm than good.

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