How to Tell if a Car Ignition Coil is Faulty?

[Bernice]

Methods to check if a car ignition coil is faulty: 1. Visual inspection—check for cracks in the insulation cover; 2. Look for any leakage of insulating materials, such as asphalt, around the ignition coil; 3. Verify whether the high-voltage damping wire can be smoothly inserted and removed from the high-voltage damping wire hole; 4. Check if the terminals of each high-voltage damping wire are properly welded; 5. Ensure the additional resistor is intact; 6. Use a multimeter in resistance mode—connect the red probe to the ignition coil terminal and the black probe to another terminal. If the multimeter needle deflects to the right, the primary coil is functional. If the needle does not move, the primary coil is open-circuited.

[McElias]

I've been repairing cars for over a decade and often encounter issues with ignition coils. The most obvious symptom of a faulty ignition coil is severe engine shaking, especially at idle - it's like the engine has asthma, wheezing intermittently. During acceleration, it's particularly noticeable; when you press the gas pedal, the car lacks power, feeling like the power delivery is inconsistent, making hill climbs especially difficult. The simplest method is to start the car and unplug each ignition coil connector one by one. If the engine sound doesn't change when you unplug a particular one, that ignition coil is dead. You can also check the coil housing for cracks or burn marks - touch it with your hand, excessive heat is definitely abnormal. Remember to perform regular inspections, as a faulty ignition coil can also cause fuel consumption to skyrocket and increase engine carbon buildup, which isn't worth the trouble.

[StThomas]

Last month, my car suddenly jerked when accelerating, and the engine malfunction light came on. I searched online and found it might be an issue with the ignition coil, so I tried checking it myself. At night, I drove the car to a dark place, started the engine, and then crouched near the engine to observe. Normally functioning ignition coils show a blue-purple electric spark, but I noticed almost no spark in the third cylinder, confirming the coil was faulty. I also smelled gasoline, likely due to incomplete combustion. Later, at the repair shop, a diagnostic tool confirmed misfiring in the third cylinder. The mechanic explained that a faulty ignition coil leads to incomplete combustion of the air-fuel mixture, and prolonged neglect could even damage the catalytic converter, so it needed immediate replacement.

[DeKeira]

After driving for a long time, you'll notice signs of a faulty ignition coil. The most obvious symptom is engine shaking, resembling a misfire, especially during cold starts when the vibration is more pronounced. Sometimes the engine warning light suddenly illuminates—don't rush to dismiss it, as it may indicate ignition issues. During acceleration, the car lacks power, struggles to increase RPM, and overtaking becomes difficult. At idle, the exhaust pipe makes a sputtering noise, and the exhaust fumes smell particularly strong. When I notice these signs, I immediately head to the repair shop. The mechanic removes the ignition coil and tests its resistance with a multimeter—normal values should be around 0.8 ohms; significantly higher or lower readings indicate coil aging. Remember not to ignore these problems, or fuel consumption will skyrocket.

[VanWeston]

As a car enthusiast, I have experience with ignition coil failures. When you step on the gas but the power response is sluggish, with the RPM stuck at 3000 and unable to climb, it's most likely a faulty ignition coil. I personally use an OBD scanner to connect to the car's computer and read the fault codes. If it shows a misfire code like P0301, it directly points to the problematic coil. You can also observe the performance when the engine is warm: if the idle is unstable during cold starts but stabilizes after warming up, it indicates the ignition coil's performance degrades under high temperatures. Regular checks are crucial because insufficient ignition energy can lead to spark plug carbon buildup, which in turn accelerates coil aging, creating a vicious cycle.