How to Determine if an Ignition Coil is Faulty?
3 Answers
To determine if an ignition coil is faulty: When the car is idling, if the shaking sensation is very noticeable, you can observe the exhaust pipe outlet. If the exhaust gas shows obvious intermittency and you can hear a sputtering sound, it can basically be concluded that the ignition coil is faulty. The reason the ignition coil can convert the low-voltage electricity in the car into high voltage is due to its similar form to a regular transformer, with the primary coil having a larger turns ratio than the secondary coil. However, the working method of the ignition coil differs from that of a regular transformer. A regular transformer operates at a fixed frequency of 50Hz, also known as a power frequency transformer, whereas the ignition coil operates in a pulse form and can be considered a pulse transformer. It repeatedly stores and releases energy at different frequencies based on the engine's varying speeds.
Previously, when the ignition coil in my car failed, the vehicle shook violently and had poor acceleration. To determine if it's faulty, first observe the symptoms: the engine vibrates severely at idle or during acceleration, as if the entire body is shaking; fuel consumption suddenly increases, costing a lot of money; and abnormal exhaust emissions may produce black smoke. The self-inspection method is simple: open the hood and carefully inspect the ignition coil's appearance for any cracks or burn marks, then feel its temperature with your hand to check if it's even—coils that are cold or excessively hot usually have issues. If unsure, visit a professional auto repair shop to measure the resistance value with a diagnostic tool; the normal range is between 1 and 2 ohms. I recommend not ignoring this issue, as a faulty coil can also damage the spark plugs, significantly increasing repair costs. Regular maintenance, such as cleaning the ignition system, can prevent similar faults. Driving habits are also crucial; avoid frequent short trips and starts to reduce stress on the coils.
I have a set of steps to determine the condition of ignition coils when repairing my car: First, let the engine idle and listen for any crackling abnormal noises, while observing whether the dashboard warning light comes on. Then, use a multimeter to measure the coil resistance: disconnect the wiring, attach the probes properly, and if the reading falls outside the standard range (e.g., 0.5 to 1.5 ohms), the coil is faulty. If you don't have tools, you can try swapping the coil positions—move the suspected faulty one to another cylinder and see if the issue follows. Coil aging is common in high-temperature or humid environments, so I often perform preventive checks on the housing seals to avoid water ingress. If the problem persists, it's best not to cut corners and attempt DIY fixes; instead, have a technician diagnose it to prevent bigger issues. Also, remember to check if the battery voltage is stable, as voltage fluctuations can affect coil lifespan.
