Common Bad Ignition Coil Symptoms

Naomi O'Colman

Updated on:

Bad Ignition Coil Symptoms

Bad Ignition Coil Symptoms

An ignition coil’s job is to transform a car battery’s low current into enough power to start the engine and ignite the fuel. An ignition coil malfunction can result in a variety of mechanical and performance problems. So, what are the bad ignition coil symptoms?

What is the Function of an Ignition Coil?

Compact electrical transformers are what ignition coils are. They transform the modest 12-volt current found in automobile batteries into the considerably higher voltage required to ignite the gasoline and start the engine.

A car’s ignition coil is separate from each spark plug. The coil is either physically attached to the spark plug by wires or sits on top of the spark plug without them. To generate an electric spark that could ignite the fuel, the spark plug requires between 15,000 and 20,000 volts of power. It will result in engine misfires or poor fuel consumption if you do not have powerful ignition coils.

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A faulty ignition coil can also be caused by a low voltage or unusually high voltage battery. This can lead to a slew of other problems with the vehicle, and replacing the batteries can solve a lot of them.

Many older automobile batteries just degrade with age, and one symptom of a faulty battery is if it doesn’t read at least 12.65V when completely charged.

Common Bad Ignition Coil Symptoms

Power loss

One of the first signs of a failing ignition coil is this. Your vehicle will feel slow and have a loss of power if you do have ignition coil problems. To achieve the requisite combustion, erratic sparks are used. Take your vehicle in for maintenance if you lose power to prevent further issues that will cost you more money to fix.

Bad fuel economy

It’s a symptom of ignition coil failure if you travel the same distances but stop at the petrol station more often. An inaccurate 02 sensor read transmits more gas than is required when an ignition coil fails. Since the spark plugs don’t get enough power, the system injects additional gasoline to compensate.

Check engine light is turned on

If your car misfires or starts slowly, the check engine light will illuminate. A faulty ignition coil is frequently to blame for this problem. The best course of action is to schedule an engine diagnostic with your Cadillac expert as soon as possible before the problem becomes costly.

Stalling and rough start

To start an engine and drive a vehicle, the ignition must spark at precisely the appropriate time. It will be difficult to start the engine if an ignition coil fails and does not give the necessary voltage to the spark plugs. It could be a defective ignition coil generating erratic sparks to the spark plugs if your vehicle stalls and even shut off completely when you stop.

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A defective ignition coil could be at blame if the vehicle starts to backfire. When excess fuel in the combustion cylinders bursts, a loud bang is heard, and black smoke and a strong gas odor emanate from the exhaust pipe. The system will suffer damage if the problem is not resolved immediately.

Engine malfunction

When you speed, your vehicle will misfire due to a defective ignition coil. A misfire might cause your car to stop working while you’re driving in extreme situations. One of the cylinders may ignite erroneously or not at all, resulting in a misfire. The catalytic converter and other engine parts may be damaged as a result of the emission.

Can You Repair a Bad Ignition Coil?

It is impossible to fix a damaged ignition coil; it must be replaced. However, if the ignition coil has been polluted by an oil leak in the spark plug tube/well and the end of the ignition coil boot has not become soft, you may be able to repair its functioning by cleaning it with an electronic cleaner. However, any ignition coil that shows signs of corrosion or rust should be replaced.

The Cost of Replacing an Ignition Coil

A new ignition coil’s price is determined by the vehicle’s make and model. Coils range in price from $75 to $300. Labor charges will range from $50 to $100 per hour if you have the work done correctly.

If you take your automobile to an automotive repair shop to have your ignition coil replaced, you should budget at least $150 to $200. Expect to pay significantly more should you choose to buy from a dealership.

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Is It Possible to Replace One Ignition Coil at A Time?

Your car’s malfunctioning ignition coil can be replaced separately. As a precaution, it’s best to replace all of the ignition coils at once. This is due to the fact that when one coil dies, another isn’t far following, especially if the car has logged more than 100,000 kilometers.

If your car has a coil pack, which is a collection of ignition coils that are physically connected, you’ll need to replace the entire pack.

Can You Drive with A Bad Ignition Coil?

It is possible to drive a car with a defective ignition coil, but it is not encouraged because it may cause harm to other parts of the vehicle such as spark plugs and catalytic converter.

Clogging of the spark plugs

Misfires can occur as a result of inadequate sparking from an ignition coil malfunction, which can dirty the spark plugs.

The failure of the catalytic converter

If you drive your vehicle for an extended duration with malfunctioning ignition coils, the catalytic converter may completely meltdown. Because a faulty ignition coil causes the engine to misfire, any unburned gasoline that exits the combustion chamber ignites within the catalytic converter, causing it to overheat. Overheating can melt internal structures and clog the catalytic converter, requiring a costly replacement.


If you observe an engine hesitation or a considerable loss of performance in your car, as well as high fuel usage, you should inspect the ignition system, which includes the spark plugs, ignition coils, and connectors/wires.

It is recommended that laypeople attend a workshop in any case. A qualified mechanic can quickly identify the issue.