How can I fix a misfiring engine? CAUSES & REMEDIES

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Misfiring Engine

If you’ve ever felt a sudden jerk or shudder when driving, chances are your engine is misfiring. Engine misfiring can occur when the spark plugs fail to ignite the fuel mixture in one or more cylinders, resulting in incomplete combustion. This can lead to a variety of issues, including poor fuel economy, loss of power, and increased emissions.

Misfiring engine: New engine view
Engine assembly

Causes of Engine Misfiring:

There are several reasons why your engine might misfire, including:

  1. Faulty Spark Plugs or Ignition Coils: Worn-out or damaged spark plugs or ignition coils can prevent the fuel mixture from igniting properly.
  2. Fuel System Issues: Dirty fuel injectors or clogged fuel filters can cause the fuel mixture to be too lean or too rich, leading to incomplete combustion.
  3. Airflow Problems: If the air entering the engine is restricted, it can affect the fuel mixture and cause misfiring.
  4. Engine Mechanical Issues: Worn-out piston rings or valves can cause low compression in one or more cylinders, leading to misfiring.

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  • A spark plug socket and ratchet
  • A spark plug gap tool
  • A multimeter
  • A fuel pressure gauge
  • A compression tester


Misfiring engine Fixing: mechanic solving it.
Misfiring fixing: mechanic

Step 1: Check the Spark Plugs and Ignition Coils

The first step in diagnosing engine misfiring is to check the spark plugs and ignition coils. Remove the spark plugs with a spark plug socket and ratchet, and inspect them for wear and damage. Use a spark plug gap tool to check the gap, and adjust it if necessary.

Test the ignition coils with a multimeter to ensure they’re providing adequate voltage to the spark plugs. If you find any faulty spark plugs or ignition coils, replace them.

This is a relatively inexpensive fix and can cost anywhere from $100-$400.

Step 2: Check the Fuel System

Next, check the fuel system for issues. Use a fuel pressure gauge to test the fuel pressure, and ensure it’s within the manufacturer’s specifications. If the pressure is too low, the fuel filter or fuel pump may need to be replaced. This can cost between $50-$200.

Clean the fuel injectors to ensure they’re delivering fuel properly. You can use a fuel injector cleaner, or have them professionally cleaned.

Step 3: Check the Airflow

Check the airflow to the engine by inspecting the air filter and intake system for blockages. Replace the air filter if it’s dirty, and inspect the intake system for any clogs or obstructions. This is a relatively cheap fix, costing around $20-$50.

Step 4: Check the Compression

If the above steps don’t solve the issue, check the engine’s compression with a compression tester. Low compression in one or more cylinders can cause misfiring. If the compression is low, the engine may need to be repaired or rebuilt.

This can cost anywhere from $500-$2,500, depending on the severity of the issue.


diagnosing and fixing engine misfiring can require a combination of tools and steps. If you’re not comfortable performing these checks yourself, it’s best to have a professional mechanic perform the diagnosis and repair. By addressing the issue promptly, you can avoid further damage to your engine and ensure your safety on the road.

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