Bad Ignition Coil Symptoms and Replacement Cost

Modern car models are equipped with internal combustion engines that need electricity to run smoothly. Ignition coils supply power to the electrical components of the vehicle. If you have a damaged ignition coil, you may find it hard to jump-start the engine. 

The reason is ignition coils provide sufficient power to the fuel to start the engine. If the ignition coils in your car are defective, it may affect the vehicle’s overall performance and cause numerous mechanical issues.

To avoid this, make sure the ignition coils are functioning in good condition. You will be able to know if your auto has a defective ignition coil by looking out for symptoms we will be talking about in detail in this post.

Understanding The Ignition Coil

Before we figure out the signs that cause bad ignition coils, let’s gain an insight into the use of ignition coils and how it works. Ignition coils, also known as Spark coils, play a significant role in getting your vehicle’s engine started.

The car battery has a very low voltage, which is not enough to get the engine started. The ignition coils take this voltage, convert it into thousands of volts, and send it back to the spark plug. 

Without this huge energy, it is not easy for the spark plugs to start the engine. Once the spark plugs fail to ignite the engine, you know that the culprit has to be the ignition coils. 

How Do Ignition Coils Function?

Ignition coils work as compact electrical transformers that convert the 12 V current from the car battery into higher voltage to start the engine. To fuel up the combustion process, the coil accumulates a high energy voltage. In normal cases, the spark plug requires only 15,000 to 20,000 volts, while in some car models, it goes up to 60,000 to 75,000 volts.

If the ignition coil is not strong enough and in good condition, it may be weak fuel consumption. Defective ignition coils will provide either abnormally high voltage or low voltage to the spark plugs.

If the engine stalls, it will impact the smooth running of the vehicle the best way to fix this issue is to get the ignition coils fixed by a professional auto mechanic. 

How Do Ignition Coils Become Defective?

While ignition coils are made using durable materials, there is no guarantee that they will last forever. They tend to become defective because of the faulty plug wires or spark plugs that ignite the fuel to start the engine.

In addition to that, the engine vibration and heat produced in the combustion chamber can also cause damages to the ignition coils. Most autos do not require an ignition coil replacement until they have reached up to 90,000 to 100,000 miles. 

Bad Ignition Coil Symptoms

If your vehicle is giving you trouble and causing interruptions to the smooth ride on the road, there are some issues with the ignition coil.

Having a damaged or defective ignition coil can affect the overall performance of your automobile. You need to look out for the common symptoms that indicate a defective ignition coil.

1. Extremely low power

When it comes to defective ignition coils, loss of power is one of the common symptoms you will notice in the beginning. Cars with defective ignition coils find it hard to start the engine. Your vehicle runs slowly and gives a sluggish feel due to reduced power. 

As the power drops further, you will notice weird sounds due to the irregular sparks produced to ignite the combustion. When you notice your vehicle stalling or getting slow even after pressing down on the accelerator, please take it to the nearest auto center to fix the defective coils. Prolonging the maintenance schedule will cost you more for repairs. 

2. Reduced fuel economy

Do you take the same route and drive the same distance daily but find yourself fuelling up more often? You might notice the mileage of the car is low. What could be the reason behind it? 

If you have a damaged ignition coil, the spark plugs do not get adequate power to ignite the engine. This causes the engine to misfire, resulting in the consumption of more fuel which gets released through the exhaust pipe without even completely burning it. 

Once you notice your fuel tank getting empty faster than usual, it’s time to check the ignition coils and get them replaced to avoid escalating the issues.

3. Engine stalls and finds it hard to start

If you encounter difficulty starting the engine, it must be due to a faulty ignition coil. The ignition coil sparks the plugs to get the engine up and running in no time to start the engine. If the coils are not running properly, the coils will not be able to produce a huge amount of voltage, causing the engine to stall. 

In some cases, while the vehicle is running at an average speed, you will notice that the engine suddenly comes to a stop. This is because the ignition coil is failing and is not able to send regular sparks to ignite the fuel in the combustion. 

4. Engine Misfires

Does your engine stall or misfire when you suddenly accelerate or stop your car? This must be due to the improper functioning of the ignition coil. In most cases, the misfires may appear to be strong jerks or vibration or splattering noise which indicates the engine cylinders are not firing sparks correctly.   

This symptom is noticed during the initial stages when the ignition coil fails. Backfiring happens when the unburnt fuel from the chamber flows out through the exhaust pipe, leaving behind traces of oil on the road.

If the issue is not rectified immediately, it can impact the other parts of the engine and exhaust system, including the catalytic converter. 

Average Ignition Coil Replacement Cost

The average cost of a new ignition coil is between $200 and $280. Some coils cost $75 while others cost $300. Professional labor for replacement costs between $50 and $100 per hour. An auto repair store will charge between $150 and $200.

Final Thoughts

To keep your car running in good condition without the engine stalling, you need to ensure that the ignition coils are working well. If you notice any of the above faulty ignition coil signs, get them replaced as soon as possible. 

Liam Dare

As CEO of, my passion for the automotive world motivates me to build online businesses that provide information and entertainment to users. I am proud to contribute in a positive way to the automotive community.