The ignition coil in your vehicle is an important part of its ignition system. It draws voltage from the car’s battery and amplifies it before sending it to the spark plug for firing the engine. The current article provides details on how to detect and replace a faulty ignition coil.

How to Detect a Faulty Ignition Coil

The following are the key symptoms that will help you detect a faulty or damaged ignition coil:

Difficulty in Starting the Engine

If your vehicle has a faulty or damaged ignition coil, it will not start easily. This is because the ignition coil is unable to provide enough power to the spark plug to fire the engine. The problem will become more aggravated in cold weather and winters. If the ignition coil has a one-per-plug system, then you will face more difficulties. Hence, if your vehicle’s engine does not start easily, then you must check the ignition coil for any damage.

Engine Stalling

Engine stalling refers to a situation when the engine is underpowered. It will feel very sluggish to drive such a vehicle. You will experience that the engine suddenly stops and starts stalling.

How to Detect and Replace a Faulty Ignition Coil?

It will be difficult for you to get complete control of the car while driving. While driving such a sluggish and stalling car is frustrating, it can also be dangerous. When the ignition coil becomes weak or damaged, it sends irregular sparks to the spark plugs. This means that the electrical charge provided will fluctuate and this prevents the engine to run smoothly and function optimally. You must immediately get your ignition coil checked by a good mechanic and replace it if needed.

Reduced Fuel Economy

You can experience a drastic reduction in fuel economy in your vehicle if it has a faulty or damaged ignition coil. A weak ignition coil will be unable to provide enough power to the spark plugs to keep the engine running smoothly. Your vehicle’s system compensates for this lack of power by injecting more fuel. This is a way to keep the vehicle running smoothly by burning extra fuel. This will increase your cost of running the car significantly. Another downside of reduced fuel economy is that it increases the carbon footprint of your vehicle which is not eco-friendly and is harmful to the environment.


You can easily know when your vehicle backfires. A failing ignition coil does not ensure complete and efficient fuel combustion. It leaves unburnt fuel in the combustion chamber. These unburnt fuel particles enter the exhaust system of the car with a high energy charge. These high energy particles are then released through the car’s exhaust pipe with a loud noise, known as exhaust backfire.

How to Detect and Replace a Faulty Ignition Coil?

A strong blast will occur through the exhaust pipe, billowing black smoke and firmly pushing the car forward. During an exhaust backfire, the check engine light may illuminate on your car’s dashboard. You may also feel the smell of petrol coming from your car.

Sometimes low fuel pressure can also cause exhaust to backfire. However, on most occasions, a faulty or damaged ignition coil is the culprit for exhaust backfire.

Occasional Idling

If you experience sudden idling of your car while driving, then it can be a symptom of a failing or already damaged ignition coil. You will also feel that the vehicle is underpowered and sluggish to drive. You can also experience heavy vibrations and knocking while driving the vehicle.

How to Detect and Replace a Faulty Ignition Coil?

This can make it difficult to drive and control, especially in heavy traffic. While this can be caused by other mechanical problems in the car, it is highly recommended to check the condition of the ignition coil, when faced with such a situation. Replacing a faulty ignition coil is relatively inexpensive and can prevent any damage to other systems and parts of your car.

How to Replace an Ignition Coil

Replacing a faulty ignition coil is a relatively simple and inexpensive process. You can do it on your own with a little effort. You will need some basic tools like a socket set and ratchet, screwdrivers, wrenches, and the ignition coil. It can help you save money which you would have paid to the mechanic for installing the new ignition coil. The following are the key steps to be followed for replacing an ignition coil:

Disconnect the Battery

The first step in changing a faulty ignition coil is to disconnect the battery. You need to disconnect the negative battery cable to cut the power to the engine. Use a socket or wrench to unscrew the clamp bolt that holds the cable to the power terminal. You must always disconnect the battery before working on any electrical system in your vehicle.

Spot the Ignition Coils

Once the battery has been disconnected, the next step is to locate the ignition coil. Generally, the ignition coil will be placed on the top of the engine. Ignition coil will be attached to the engine block or surrounding components.

Disconnect and Remove the Ignition Coil

You should now proceed to disconnect the ignition coil. You will need to disconnect the clamp bolt that attaches the ignition coils to the vehicle. The electrical connectors on the ignition coil should also be disconnected. Depending upon the make and model of your vehicle, you will need to decide which connections need to be broken first. You can refer to your vehicle’s user manual for getting more details on this. Ignition coils that have multiple plugs from one coil will have several electrical connectors. Before disconnecting these connectors, you should mark them which will make it easy for you to assemble them back again. The correct electrical wires need to be attached to the corresponding connections on the new ignition coil. Once the old ignition coil has been disconnected, you must remove it from the vehicle.

Install the New Ignition Coil

The next step is to install the new ignition coil in your vehicle. You must connect the new ignition coil exactly the reverse order in which you removed the old ignition coil. The electrical connectors that were disconnected last, should be reconnected first for the new ignition coil. While reconnecting the new ignition coil, you must ensure that the correct electrical connectors are being reattached to the new coil.

Reconnect the Battery

Now that the new ignition coil has been installed, it is time to reconnect the vehicle’s battery. Start by hand tightening the electrical connection first and then use a socket or wrench to further tighten the terminal bolt. You must be careful not to over-tighten the bolts. Doing so can damage the bolts and it is generally difficult to find them instantly. The bolts should be tightened just enough to prevent any engine vibration that could loosen the bolts again. Close the hood of the vehicle after reconnecting the battery.

Test the Newly Installed Ignition Coil

The last step of replacing the ignition coil is to test the newly installed coil. You should start the engine and check if it starts normally without any difficulties. Observe the engine noise and vibration. If the engine is running smoothly, without any vibrations and unfamiliar loud noises, it means the new ignition coil is working perfectly. You can take a test drive of the car to ensure it is running smoothly.

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