Yes, a bad ignition coil is a very common reason a car won't start. The ignition coil is a critical component of your vehicle's ignition system. Its job is to transform the battery's low voltage (12 volts) into the thousands of volts needed to create a spark at the spark plug. If a coil fails, it can't generate this powerful spark. Without a spark, the air-fuel mixture in the engine's cylinders won't ignite, and the engine simply cannot run.
A single faulty coil in a multi-cylinder engine will often cause a misfire—where the engine runs rough, shakes, and loses power—but the car may still start. However, if the vehicle has a single coil (or a coil pack) that serves all cylinders, its complete failure will result in a total loss of spark, leading to a no-start condition. The engine will typically crank normally but will not fire up. Other symptoms pointing to a bad coil include a check engine light, poor fuel economy, and backfiring.
Diagnosing this issue requires some basic mechanical knowledge. You can visually inspect the coil and its wiring for cracks or carbon tracking (black burn marks). The most accurate method is to check for spark using a spark tester or to test the coil's primary and secondary resistance with a multimeter, comparing the readings to your vehicle's service manual specifications.
| Symptom | Why It Happens | Common in Vehicles With... |
|---|
| Engine cranks but won't start | Complete loss of spark to all cylinders | Single coil, distributor systems, or failed coil pack |
| Check Engine Light with misfire codes (e.g., P0300) | One cylinder isn't firing correctly | Individual coil-on-plug systems |
| Rough idle, loss of power, shaking | Misfire from one or more cylinders not firing | All systems, but car may still be drivable |
| Poor fuel economy | Unburned fuel passes through the exhaust | A persistent misfire from a failing coil |
| Backfiring | Unburned fuel ignites in the exhaust system | Severe misfire condition |
Replacing a bad ignition coil is usually a straightforward repair. It's often recommended to replace all coils if one fails, especially if they are original and have high mileage, as others are likely near the end of their service life.
