Understanding Ignition Coils: Symptoms of Failure and Testing Tips

Mobile Mechanic tips near Wagner, TX plus more services

we’re delving into the vital role of ignition coils, their function in your vehicle, and how to identify symptoms of their failure. Ignition coils play a pivotal role in your car’s ignition system, and their primary function is to convert the low voltage of 12 volts from the battery into a high voltage of up to 40,000 volts. This high voltage is then transferred into the spark plugs, allowing them to produce the spark necessary to ignite the air-fuel mixture.

Now, there are different types of ignition systems out there, but today, we’ll focus on the coil-on-plug system, as it’s the most commonly used. The precise location of the ignition coils depends on the type of engine you have. In a 4-cylinder engine, you’ll typically find them lined up at the top of the engine in a row of 4. In a 6 or 8-cylinder engine, the ignition coils are usually arranged in rows of 3 or 4, positioned either on the left and right sides of the engine or on the front and back sides.

Let’s move on to identifying symptoms of a failing ignition coil:

Engine Light: When an ignition coil is failing to send voltage through the spark plug, it results in no spark for that specific cylinder. This leads to a misfire or a lack of a mini explosion in the combustion chamber. The engine control module detects this misfire and activates the check engine light.

Misfire Codes: Specific misfire codes will correlate with the cylinder that’s experiencing the issue. For instance, “P0302” indicates a misfire in cylinder 2. In some vehicles, there are dedicated codes for a faulty ignition coil. To read these codes, you’ll need an OBD2 scanner.

Rough Idle: The misfire caused by a failing ignition coil will lead to engine vibrations and possibly even make your steering wheel shake, particularly when your car is at a standstill.

Poor Performance:  A single misfiring cylinder can significantly affect your car’s overall performance. In a 4-cylinder engine, if just one cylinder misfires, your engine’s efficiency is reduced by a quarter, resulting in poor performance.

Smell of Gas: When the air-fuel mixture isn’t ignited in the cylinder, unburnt fuel exits through the exhaust, producing a noticeable smell of gas. It’s crucial to address this promptly as continued exposure of your catalytic converter to excess fuel can cause overheating and damage.

When inspecting an ignition coil, ensure there is no corrosion on the connectors, as this can hinder its proper functioning. Additionally, check for cracks anywhere on the ignition coil. A quick test to determine if the ignition coil is faulty involves swapping it out with another coil on the same engine. If the misfire follows the ignition coil to the new cylinder, then the coil is likely faulty and should be replaced. If the misfire remains in the original cylinder, the issue might be with the spark plug.

For further details on spark plug issues, feel free to reach out to us Mobile Mechanic

Stay informed, drive safe, and keep your engine running smoothly.


About Wagner, TX

  • Wagner: An unincorporated community in Hunt County, Texas, that was settled before 1840 and originally called Warsaw Prairie. It has a population of 58 in 2000 and is part of the Dallas/Fort Worth Metroplex.
  • Post office and school: Wagner had a post office from 1890 to 1904 and was a stop on the stagecoach route between Dallas and Shreveport. It is served by the Crandall Independent School District and has an elementary school named after W.A. Martin, a former teacher and principal in Wagner.
  • Monty Stratton: Wagner was the birthplace of major league pitcher Monty Stratton, whose attempted comeback following the loss of a leg led to The Stratton Story, starring James Stewart.
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