How to Recognize Bad Ignition Coil Symptoms

Understanding the Symptoms of a Faulty Ignition Coil

A malfunctioning ignition coil can lead to various engine problems, ranging from poor performance to complete engine failure. Recognizing the symptoms of a bad ignition coil early can prevent further damage and help maintain the smooth operation of your vehicle. This article explores the common signs that indicate a faulty ignition coil and how these symptoms can affect your engine’s performance.

A No Start condition can be caused by a bad ignition coil

When a single ignition coil fails (1st coil on the left) it can cause a no-start condition.

The engine will crank but will not fire up. This will most likely happen in an engine with a single ignition coil. However, if the vehicle has a distributorless ignition system (DIS) or a coil-on-plug system, you generally won’t see a total failure to fire up during cranking that’s related to a coil pack or coil-on-plug failure. In those cases, you’d most likely see a fire up but rough or misfiring idle or stall.

Engine Misfires Can Be Caused By a DIS Ignition Coil Or COP Coil

One of the most common symptoms of a bad ignition coil is engine misfires. The ignition coil’s primary function is to generate a high-voltage spark that ignites the air-fuel mixture in the engine’s cylinders. If the coil is failing, it may not provide a consistent spark, leading to incomplete combustion. This causes the engine to misfire, which can be felt as a stumbling or jerking sensation while driving. Misfires are often more noticeable during acceleration or when the engine is under load, such as when climbing a hill.

A Bad Ignition Coil Will Cause A Rough Idle

A malfunctioning ignition coil can cause the engine to run rough, especially at idle. You may notice the engine shaking or vibrating when the vehicle is stationary. This is often due to inconsistent spark delivery, leading to uneven combustion in the cylinders.

Difficulty Starting the Engine

A bad ignition coil can make it difficult to start your engine, especially when the engine is cold. If the coil is weak or failing, it may not generate enough voltage to create a strong spark, leading to prolonged cranking before the engine starts. In some cases, the engine may fail to start altogether.

Impact on Engine Performance: Difficulty starting the engine can leave you stranded, and repeated attempts to start a misfiring engine can drain the battery and cause additional wear on the starter motor.

Poor Fuel Economy

When an ignition coil is not functioning properly, the engine may run inefficiently, leading to increased fuel consumption. A weak or inconsistent spark can cause incomplete combustion of the air-fuel mixture, meaning that more fuel is required to produce the same amount of power. This results in lower fuel efficiency and higher fuel costs.

Check Engine Light or a Flashing Check Engine Light

Modern vehicles are equipped with an onboard diagnostics system (OBD) that monitors various engine parameters. When the system detects a problem, such as a misfire caused by a faulty ignition coil, it will trigger the check engine light on the dashboard. The check engine light is often accompanied by a diagnostic trouble code (DTC) that can be read with a scan tool, providing a clue to the underlying issue.

Loss of Power And Stuttering During Hard Acceleration

A marginal ignition coil will fail most when under heavy load. If your engine has decent acceleration when lightly applying the gas but stutters and misfires under hard acceleration, that can be caused by a bad ignition coil. This occurs because the engine is not receiving the necessary spark to ignite the air-fuel mixture in all cylinders, leading to reduced engine output. The vehicle may feel sluggish or unresponsive when you press the accelerator.

Backfiring and Popping Noises

A faulty ignition coil can cause the engine to backfire, which is characterized by a loud popping noise from the exhaust or intake system. Backfiring occurs when unburned fuel is ignited outside the combustion chamber, usually in the exhaust manifold or muffler. This can happen if the ignition coil fails to ignite the air-fuel mixture at the correct time, allowing fuel to build up and ignite suddenly.

Increased Emissions

A bad ignition coil can lead to increased emissions due to incomplete combustion. When the air-fuel mixture is not fully burned in the engine, it results in higher levels of hydrocarbons and carbon monoxide in the exhaust. This can cause your vehicle to fail emissions tests and contribute to environmental pollution.

See this post for information on how to test an ignition coil

©, 2020 Rick Muscoplat