What Is Engine Misfire : Causes, Symptoms & Solutions

engine misfire

Many times, the problem of cylinder misfire occurs in the internal combustion engine. The engine is an important part of the vehicle because it provides power to move the vehicle and operate other components. But sometimes, due to some reason, the engine starts misfiring, which has a bad effect on the power performance of the engine, due to which the problems of vibration and jerk can also be seen.

In this post, we will discuss the causes of engine cylinder misfire in detail so that you can investigate the cause of the problem and try to solve it.

What is Engine Misfiring?

Engine misfire means that one or more of the engine’s cylinders do not generate enough spark or compression, causing the air-fuel mixture in the cylinder to not ignite properly, resulting in incomplete or no combustion in the combustion chamber. Engine misfires can be caused by faulty spark plugs, bad ignition coils, clogged fuel injectors, or worn cylinder sleeves.

Often, engine wear causes problems such as rough idle, reduced power, poor fuel efficiency, and increased emissions. When the engine control module detects a misfire, it triggers the “Check Engine” light and stores a diagnostic trouble code for identification and an OBD digital scanner to read this error code and investigate the cause.

Engine Misfires Causes

Engine misfires can be caused by faulty spark plugs, damaged wiring, faulty ignition coils, fuel system problems, air or vacuum leaks, compression problems, or faulty sensors.

Let us know all the causes of engine misfires in detail so that you can thoroughly investigate the reasons for engine misfires.

1. Ignition System Problems

spark plugs

If an engine is misfiring, you may have bad spark plugs, a bad ignition coil, damaged spark plug wires, or a faulty ignition control module. Any type of problem with the components of the ignition system can cause weak or absent sparks, which can cause the engine to misfire. Therefore, in the event of an engine misfire, the first thing to be checked is the ignition components. If any component of the ignition system is found to be in failure, repair or replace it.

2. Fuel System Problems

fuel filter

The fuel system is an important part of any internal combustion engine, which supplies fuel to the fuel injectors to make the engine run efficiently. But clogged fuel injectors, bad fuel pumps, restricted fuel filters, or improper fuel pressure in the fuel system can disrupt the air-fuel mixture, preventing combustion in the engine’s combustion chamber. Due to this, the problem of misfires is seen in the engine.

3. Air Intake or Vacuum Leak


The air intake and vacuum system play a vital role in the efficient operation of any internal combustion engine. But if a leak occurs in the engine’s air intake system or vacuum lines, it can disturb the air-to-fuel ratio, impairing fuel combustion and causing engine misfires. So check for leaks in the air intake and vacuum system in case the engine misfires.

4. Compression Issues

Damage piston rings

Compression is absolutely necessary for an internal combustion engine, so that the fuel combustion process in the engine is complete. But if the engine has worn piston rings, damaged valves, a blown head gasket, or insufficient cylinder compression, the engine can have a compression problem, which can result in engine misfires. Damage to the internal parts of the engine is a sign of a serious problem, as this problem cannot be fixed without opening the engine.

5. Faulty Sensor

camshaft position sensor

Sensors in the engine monitor the function and condition of engine parts and transmit the received data to the Engine Control Module of the vehicle, from which the ECU of the vehicle determines the proper amount of fuel and correct ignition timing for efficient engine operation.

But a faulty mass airflow sensor, crankshaft, or camshaft position sensor can provide incorrect data to the engine control module, which can lead to poor fuel combustion and engine misfires.

6. Engine Control Module Issue

Faulty ECM/ECU

The ECM in vehicles is responsible for managing the engine and other systems, ensuring they function efficiently. But a faulty engine control module can result in disrupted fuel delivery as well as faulty ignition timing. As a result, the engine may misfire due to issues with other electronic components.

7. Faulty Spark Plugs

Oil On Spark Plugs

Spark plugs are a vital component of the operation of an internal combustion engine, producing a spark to ignite the fuel in the engine’s combustion chamber. But if the spark plugs in an engine are bad, then it disrupts the fuel combustion process of the engine. Due to this, the engine starts misfiring. Therefore, the first thing to check if spark plugs is bad.

8. Wiring Issues

Sometimes engine misfiring can also be caused by damaged wiring, which disrupts the functioning of engine parts and sensors. Damaged wiring can cause the sensor to be unable to send correct data to the Engine Control Module, and the ECU may manipulate the air fuel ratio based on incorrect data.

Engine Misfires Symptoms

  • Check Engine Light
  • Rough Idle
  • Loss of Engine Power
  • Poor Fuel Efficiency
  • Acceleration Hesitation
  • Increased Exhaust Smoke
  • Engine Vibration & Jerks
  • Unusual Engine Sound
  • Engine Stalling

How To Fix Engine Misfires (Solutions)

  • Check Diagnostic Codes: If the check engine light in the dashboard is on, use the OBD-II scanner to check for trouble codes associated with the misfire. This code will refer to the problem with the cylinder in the engine that is causing the misfire and the possible causes.
  • Inspect The ignition components: Often, bad spark plugs, faulty ignition coils, or damaged ignition wires are common causes of engine misfires. So remove the spark plugs from the engine and inspect them for signs of wear, deposits, or damage. If the spark plugs are not cleanable or are worn or damaged, replace the spark plugs with new ones. Also check the ignition coil and wire; if necessary, replace them with new ones.
  • Ispect Fuel Pumps and Injectors: Fuel injectors deliver fuel to the cylinders. If an injector is clogged or corroded, it interrupts the supply of fuel to the engine’s combustion chamber and can cause a misfire. In this case, it may be necessary to clean or replace the faulty injectors.
  • Check Compression: In many cases, misfires can be caused by low compression in the engine cylinders. You will need a compression tester to measure cylinder compression. If the compression in the affected cylinder is significantly lower, this may indicate a mechanical problem such as damaged piston rings or valves.
  • Check for Air Intake and Vacuum Leaks: A vacuum leak can disrupt the air-fuel mixture. Inspect vacuum hoses, gaskets, and other components for leaks. Identify vacuum leaks by spraying around potential leak points while the engine is running. If the engine RPM changes, this indicates a vacuum or air intake leak.
  • Check Sensors: Malfunctioning sensors, such as the crankshaft position sensor or camshaft position sensor, can affect the fuel combustion process in the engine and cause engine misfires. So check the sensor and connections. For this, you can use an OBD scanner.
  • Check Throttle Body: If your vehicle’s throttle body is dirty or damaged, it can cause engine misfires. So clean the throttle body, if you find any defects after cleaning, replace it with a new one.


Q. Can I drive with a misfire?

You can drive with a misfire for a temporary period of time. But driving with a misfire is not safe and can damage your engine. Your vehicle will consume more fuel due to an engine misfire.

Q. Can a misfire fix itself?

If your vehicle has a spark plug related misfiring, you can correct the misfiring by cleaning or replacing the spark plugs. But if there are any other problems, they definitely won’t fix anything until you take the car to a mechanic.

Q. How much does it cost to fix a car fire?

Depending on the cause of the misfire, the cost of repair and replacement can be anywhere between $120 to $1,200. Generally, the cost of repairing an engine malfunction depends more on the model of the vehicle and the parts being repaired or replaced.

Share If You Like

Leave a Comment

error: Content is protected !!