When the smooth performance of the Volkswagen suddenly changes into rough idling, sluggish acceleration, and a flashing check engine light, then a failing ignition coil is the main reason. This minor component plays a very crucial role in a car’s engine, converting the low-voltage battery power into the high-voltage spark that is necessary for combustion.
Understanding the signs of ignition coil failure and why they happen is key to keeping your Volkswagen running smoothly and avoiding more expensive repairs down the road.
Common Causes of Ignition Coil Failure
- Worn-out Spark Plugs: This is one of the common reasons. Over time, the gap in the spark plug widens. This forces the ignition coil to work harder and generate more voltage to jump the larger gap, causing the coil to overheat and wear out faster.
- Engine Overheating and Vibration: Excessive heat is a significant threat to the ignition coil’s sensitive internal components. Prolonged exposure to high temperatures can degrade the coil’s wiring and insulation, causing internal short circuits. A constant engine vibration can damage the coil’s internal structure.
- Oil or Coolant Leaks: In vehicles with coil-on-plug systems, leaks from the valve cover gasket can allow oil or coolant to seep into the spark plug tubes. This fluid contamination can cause electrical shorts and corrosion, damaging the coil and interfering with its ability to generate a spark.
- Electrical Problems: Issues with the car’s electrical system, such as a weak or aging battery, a faulty alternator, or bad wiring, can impact the coils. An inadequate voltage supply can force the coil to overwork, causing premature failure.
- Age and Wear: Ignition coils have a lifespan. Under ideal conditions, they will wear out from repeated use. This is a natural part of the vehicle’s maintenance cycle.
Recognizing the Symptoms of Failure
- Engine Misfire and Rough Idling: A misfire occurs when a cylinder fails to fire correctly, resulting in a sensation that the engine is coughing or sputtering. When the car is idle, it gives a rough, shaky, or unstable sensation.
- Loss of Power and Poor Acceleration: A compromised ignition system can cause the engine to lose power, leading to sluggish acceleration and reduced performance. This can cause difficulty in gaining speed when merging onto a highway or climbing a hill.
- Decreased Fuel Efficiency: A failing coil causes incomplete combustion of the fuel-air mixture. To compensate, the engine’s computer may inject more fuel, resulting in a significant drop in gas mileage.
- Check Engine Light: The car’s onboard diagnostic system will detect misfires and other ignition irregularities that can trigger the check engine light. A flashing check engine light can indicate a severe misfire that requires immediate attention.
- Difficulty starting or stalling: If an ignition coil fails, then the engine may not be able to start at all. The intermittent coil failure can cause the engine to stall when idling or driving at low speeds.
- Backfiring and Black Exhaust Smoke: Unburned fuel from a misfiring cylinder can enter the exhaust system, resulting in backfiring and black exhaust smoke. This can cause a loud backfire or pop as the raw fuel ignites in the hot exhaust. It can result in black smoke and a strong smell of gasoline coming from the tailpipe.
Diagnosing and Solving Volkswagen Ignition Coil Failure
Conduct a Visual Inspection
Take a closer look at the ignition coils. Overheating or fluid leaks can cause visible cracks or burns on the coil body. Checking the spark plug well for oil or coolant, as this contaminant can damage the coil.
DIY Replacement
- Ensure the engine is completely cool and disconnect the negative battery terminal.
- Remove the engine cover, which is usually held in place by friction-fit grommets.
- Disconnect the electrical connectors by pressing the retaining tab and sliding it back. Gently twist and pull the old coil straight up to remove it from the spark plug well.
- The worn spark plugs can cause the coils to fail. Therefore, it is recommended to replace them simultaneously. Use compressed air to clean any debris from the well before removing the old plug.
- Apply a small amount of dielectric grease to the inside of the new coil’s boot to ensure a good seal. Push the new coil into place over the spark plug until it clicks into position.
Bavarium Autoworks: Your Trusted Partner for Volkswagen Ignition Coil Repair
Addressing ignition coil failure promptly is crucial for 
maintaining Volkswagen’s performance, which can prevent more extensive engine damage and ensure a safe driving experience. The DIY approach can work for some minor repairs, but for significant maintenance, professional diagnosis is often necessary. If you are in the Mountain View, CA area and experiencing any of the symptoms of a failing ignition coil, then you can trust the experts at Bavarium Autoworks. Our certified technicians and commitment to quality service ensure that we can accurately diagnose the problem and perform the necessary repairs with precision, getting your Volkswagen back on the road smoothly.