What Are the Signs of a Bad Ignition Coil?

What Are the Signs of a Bad Ignition Coil? | Oceanworks Berkeley

The engine's ignition coil is responsible for converting the low voltage from your car’s battery into the high voltage needed to create a spark in the spark plugs. This spark ignites the air-fuel mixture in your engine, powering your vehicle down the road. However, like any part, ignition coils wear out over time, leading to a host of engine performance issues. So, how can you tell if your ignition coil is on its last leg?

Trouble Starting the Engine

If your car is having a hard time starting, especially on those chilly mornings, a faulty ignition coil could be the culprit. The ignition coil provides the necessary spark to start the engine, so if it’s not functioning properly, your engine may struggle to turn over. You might hear the starter cranking, but the engine just won't catch. Often, this is due to an inconsistent or weak spark, which can leave you stranded at the worst possible times.

Misfiring and Poor Acceleration

One of the most noticeable symptoms of a bad ignition coil is engine misfiring. If you’re driving and feel a sudden jerk or hesitation, that’s a sign your engine isn't firing on all cylinders. A faulty ignition coil can cause intermittent misfires, which means some of your cylinders aren’t getting the spark they need. This can lead to rough idling, a drop in engine power, and poor acceleration. If you've noticed your car has become sluggish when you hit the gas pedal, it’s worth getting your ignition system checked out.

A misfiring engine doesn't just affect your driving experience; it can also cause long-term damage to other engine components. Left unchecked, it can result in unburned fuel entering your exhaust system, which might damage your catalytic converter—a repair that’s both time-consuming and costly.

Check Engine Light Illuminated

No car owner likes seeing the dreaded "check engine" light pop up on their dashboard. But did you know that a failing ignition coil is one of the reasons that light could turn on? Your vehicle’s onboard computer constantly monitors engine performance, and if it detects a misfire or irregularity due to a bad ignition coil, it’ll trigger the check engine light.

Of course, the check engine light can illuminate for various reasons, so it's best to use a diagnostic tool or visit a professional to pinpoint the exact issue. However, if this light appears alongside any of the other symptoms mentioned, there's a good chance your ignition coil could be to blame.

Reduced Fuel Efficiency

Are you finding yourself at the gas pump more often than usual? A bad ignition coil can wreak havoc on your car’s fuel efficiency. When the ignition coil isn’t firing correctly, it can cause incomplete combustion, leading to wasted fuel. Your engine has to work harder to compensate for the lack of power, which means burning more gas than necessary. If you’ve noticed a sudden drop in your car's miles per gallon, it might be time to investigate the health of your ignition coils.

Engine Stalling

Another warning sign of a failing ignition coil is engine stalling. This can happen when you’re idling at a stoplight or even when you’re driving down the highway. A faulty ignition coil can cause irregular sparks, leading to engine interruptions that make your car stall unexpectedly. Stalling can be dangerous, especially in heavy traffic, so it's crucial to address this issue before it leads to an accident.

Unusual Engine Sounds

Your car might start making some strange noises if the ignition coil is failing. Listen for popping or sputtering sounds coming from the engine compartment. These sounds usually occur when unburned fuel ignites in the exhaust system, a direct result of an inconsistent spark from a bad ignition coil. Ignoring these unusual sounds can not only damage your engine further but also lead to costly repairs.

Increased Exhaust Emissions

A faulty ignition coil can cause your car to produce higher levels of emissions. If the coil isn’t providing enough spark, the fuel may not burn completely in the combustion chamber. This leads to an increase in hydrocarbon emissions, which can cause your car to fail an emissions test. For those living in areas with strict emission regulations, this can be a significant issue. If you notice darker exhaust smoke or a strong fuel smell, it might be a sign that your ignition coil is failing.

The Importance of Timely Repair

While it might be tempting to ignore these signs, a failing ignition coil can lead to more serious engine problems if not addressed. Regular vehicle maintenance is key to preventing ignition coil failure. If you suspect your ignition coil is failing, it’s best to get it checked and replaced promptly to avoid further damage.


Noticing misfires or a drop in fuel efficiency? It could be your ignition coil! Schedule an appointment with Oceanworks Berkeley today. We specialize in diagnosing and repairing ignition system issues to keep your car running smoothly.

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