How do I know what ignition coil I need?

Signs of a Bad Ignition Coil

1. Illuminated Check Engine Light

With most modern vehicles, a faulty ignition coil is enough to turn on the Check Engine Light. If you have an OBD-II diagnostic scanner, you may see a P0351 ignition code. Of course, because all cars are different, an ineffective ignition coil may register a different code for the problem. Alternatively, you may see a code for an engine misfire, which could be the result of a dead ignition coil.

2. Misfiring Engine

If an ignition coil is not working properly, your engine will likely misfire. A misfiring engine results in a jerking or sputtering feel when you are moving at normal speeds. When you stop, a misfire from a bad ignition coil may cause your vehicle to run roughly, vibrate or shake.

3. Hard Starts

To run, your vehicle’s engine needs a spark at the right time. If a spark plug is not getting the right voltage to create a spark, you may experience a hard start. This may mean the ignition coil is not working properly. While this problem can happen with any coil configuration, it is more common with engines that have a single ignition coil.

4. Worsening Gas Mileage

Ignition coils can either fail completely or fail intermittently. This means that you may have a coil that goes bad over time. Accordingly, even if your vehicle seems to be performing normally, you should watch for worsening gas mileage. Even if it is not caused by a bad ignition coil, decreasing gas mileage is a sure sign that something is wrong.

5. Diminished Power

Vehicles with bad ignition coils often run roughly. This means, when your vehicle is idling, you may notice a rough feel or sound. Your vehicle may also experience a drop in power. As a result, a bad ignition coil can make it acceleration more sluggish. The vehicle may even stall.

6. Sudden Backfires

Modern engines should not backfire. This loud bang happens when unburned fuel suddenly escapes out of the exhaust system. While there are a few causes of backfires, a failing ignition coil is a common one. Regrettably, if you do not address backfires quickly, they can lead to significant engine damage.