Common Signs of a Faulty Ignition Coil and How to Troubleshoot

by:Haiyan     2023-09-08

Common Signs of a Faulty Ignition Coil and How to Troubleshoot


The ignition coil is a vital component of a vehicle's ignition system, responsible for converting low voltage power into high voltage electricity needed to create a spark in the spark plugs. When the ignition coil starts to malfunction, it can lead to several problems that can affect the performance and reliability of the vehicle. In this article, we will discuss some common signs of a faulty ignition coil and provide troubleshooting tips to help you diagnose and resolve the issue.

1. Random Stalling and Misfiring

One of the earliest signs of a faulty ignition coil is random stalling or misfiring. The ignition coil sends voltage to the spark plugs, which in turn ignites the fuel-air mixture in the combustion chamber. When the coil is faulty, it may fail to provide the necessary voltage consistently, resulting in a weak spark or no spark at all. This can cause the engine to misfire, resulting in a rough running engine, loss of power, and even stalling while driving.

2. Difficulty Starting the Engine

Another common sign of a faulty ignition coil is difficulty starting the engine. When an ignition coil starts to fail, it may not generate sufficient voltage to create a spark in the spark plugs, making it harder for the engine to start. You may have to turn the key multiple times or crank the engine for an extended period before it finally starts. If you notice that your vehicle is becoming harder to start, it could be an indication of a faulty ignition coil.

3. Decreased Fuel Efficiency

A faulty ignition coil can also lead to decreased fuel efficiency. When the coil fails to deliver the necessary voltage to the spark plugs consistently, incomplete combustion may occur. This can result in poor fuel efficiency as the engine struggles to burn the fuel-air mixture efficiently. If you notice a sudden drop in your vehicle's fuel economy, it is worth checking the condition of the ignition coil.

4. Engine Surges or Hesitates

If you experience engine surges or hesitations while driving at a consistent speed, it could indicate a faulty ignition coil. When the coil is failing, it may cause intermittent interruptions in the spark generation, resulting in irregular combustion in the engine. This can cause the engine to surge or hesitate, making it difficult to maintain a steady speed. Ignoring this issue can lead to long-term damage to other engine components, so it is crucial to address it promptly.

5. Illuminated Check Engine Light

A malfunctioning ignition coil may trigger the vehicle's onboard diagnostic system and cause the check engine light to illuminate on the dashboard. Modern vehicles are equipped with sensors that monitor various engine parameters, including the performance of the ignition system. If the system detects an issue with the ignition coil, it will store a diagnostic trouble code and illuminate the check engine light. If you see the check engine light come on, it is advisable to have your vehicle diagnosed by a professional to identify the underlying cause.

Troubleshooting Steps

If you suspect a faulty ignition coil based on the signs mentioned above, you can follow these troubleshooting steps to diagnose the issue:

1. Check for Visible Damage: Inspect the ignition coil for any visible signs of damage such as cracks, corrosion, or melted wiring. Physical damage can often be an obvious indicator of a faulty coil.

2. Perform Resistance Test: Using a multimeter, you can measure the resistance of the coil. Consult the vehicle's service manual for the acceptable resistance range specific to your vehicle's ignition coil. If the measured resistance falls outside this range, it indicates a faulty coil.

3. Check Spark Plug Wires: Inspect the spark plug wires for signs of wear or damage. Faulty wires can affect the performance of the ignition coil. Replace any worn-out or damaged wires and retest the system.

4. Swap Coils: If you have multiple ignition coils in your vehicle, you can swap the suspected faulty coil with a known good one. Start the engine and see if the symptoms transfer to the different cylinder. If they do, it confirms a faulty coil.

5. Consult a Professional: If you are unable to diagnose the issue or don't have the necessary tools, it is recommended to seek assistance from a professional mechanic. They have the expertise and specialized diagnostic equipment to accurately identify and resolve ignition coil problems.


A faulty ignition coil can lead to various issues that can affect the performance, reliability, and fuel efficiency of a vehicle. By recognizing the common signs of a failing ignition coil and following the troubleshooting steps outlined in this article, you can diagnose and resolve the issue promptly. Remember, regular maintenance and periodic inspections are essential in ensuring the optimal functioning of the ignition system and the overall health of your vehicle.

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