As time passes and the mileage on your car increases, some parts might wear out and completely fail. It includes parts like the catalytic converter or the ignition coil. In that case, you must look for specific symptoms and know when to replace them. In the ignition system, the ignition coil supplies the necessary current to ignore the fuel mixture in the combustion chamber.
Summary
The most common symptoms of a bad ignition coil are the engine light coming on and a rough start. Replacing a bad ignition coil costs between $20 and $40.
Here’s a list of the things we’ll look at:
Table of Contents
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The ignition coil is essential for the proper functionality of your car. A bad or failing ignition coil will prevent your car from starting. Therefore it is a serious problem. In modern cars, each spark plug has its ignition coil, some of which are electronically controlled by the central computer.
Because they are so important, you must pay attention to their condition more often. In this article, we will show you 12 overheating ignition coil symptoms to look for while also informing you about the replacement cost in case they are broken.

Symptoms of a bad ignition coil
While a skilled mechanic can diagnose your car and identify the problem accurately, you can also do the same at home without the help of any special tools. All you have to do is a minimal investigation and specific focus on a certain problem.
If you suspect that the ignition coil is failing, there are a couple of symptoms you can look for and identify if your car has a problem.
Here are some of the symptoms of a bad ignition coil we’ll take a look at:
- Worn cables
- The check engine light coming on
- Poor acceleration
- Rough start
- Stalling
1. Excessive heat
Ignition coils are exposed to extreme heat from the engine since they are situated so close to it. All the plastic and metal components of the coils are constantly suffering from the heat generated by the engine.
When affected by heat, the metallic components will constantly expand. It reduces the ability to transform low voltages into high voltages. Over time your ignition coil might fail due to excessive heat.
2. Excessive vibrations
Besides heat, the engine also produces significant vibrations when running. If you are driving off-road or on a bumpy surface, the vibrations are accentuated. The effects on the ignition coil are worse. Because they are installed above the spark plugs, they are sensitive to intense vibrations.
Over time, the connections in the coil assembly will inhibit the current flow between the components of the coil. That is why you must bring your car to an auto repair shop every once in a while for a proper check-up and diagnosis.

3. Moisture and contamination
Moisture and contamination can often cause wear. Because these are installed in the engine, they will get contaminated if oil and coolant leak into the engine block. Moisture can also corrode or short the electrical components of these parts, causing them to malfunction.
If you notice leaks in the engine block, you must fix this problem as soon as possible. Not only your ignition coils are at risk, but your entire engine might be compromised if exposed to excessive moisture.
4. Excessive spark plug gap
Several conditions have to be met for the ignition coils to function properly. One of them requires that the current from the coils must bridge the gap between the plug electrodes. It will generate the spark by the spark plug and allow you to turn on your engine quickly.
But they will have to work harder if the gap is wider than recommended. Because there is an additional effort to produce a current strong enough to reach the increased gap, the coil components are stressed and can wear more quickly.
5. Worn cables
It is an older technology that you will find in some outdated vehicles. Special ignition cables deliver the current from coils to the spark plugs. Sometimes they can get damaged due to the excessive heat inside the engine block.
Over time, these cables will go bad and lose their resistance. If not replaced consistently, these cables could also burn out the ignition coil and further increase the repair cost.

6. The check engine light is on.
It is the easiest way to spot something wrong with your car. When the check engine light turns on and is visible on the dashboard, then it is a clear warning sign that there is something wrong with a component of the engine.
The onboard computer will monitor the vehicle’s systems and signal you when the ignition coils are damaged or failing. As a result, the check engine light turns on and asks you to investigate the problem.
7. Rough start
This part is directly responsible for turning on your engine. If this part fails, you will notice that the engine will struggle upon starting. In some cases, it won’t be able to start.
A significant amount of energy is delivered from the battery for starting your engine. Ignition coils are critical in meeting this high energy demand. But if the ignition coils are damaged or failing, you will often experience rough starts.
8. Poor acceleration
There are many reasons why you might experience poor acceleration when you press on the gas pedal. Faulty sensors and an incorrect fuel supply are some of them.
You should also consider the spark plugs and ignition coils to be the reason for your problem. If these parts are failing, the engine will hesitate with the acceleration process. You will be able to notice a significant delay in throttle response.
9. Stalling
When the engine is stalling, there is something likely wrong with the ignition coil. It can be caused by several issues, such as insufficient air or failure of combustion.
They are responsible for providing the necessary voltage to create a spark. When this operation cannot be done, the engine will shut down because it cannot produce enough propelling force.

10. Misfires
This symptom is similar to stalling, where the engine misfires can be linked with bad or failing coils. Suppose there is a combustion failure in the engine’s cylinders. In that case, your car will behave differently. The engine will misfire more often.
These are easy to notice because they make a well-known sputtering sound that can identify. If you can hear any uncommon noise coming from the engine block, you should have your car checked by a mechanic.
11. Backfires
As a result of misfires that happen inside the combustion chamber, the backfires will happen outside the cylinders. When ignition coils are worn out or damaged, it always leads to failure in the ignition in at least one cylinder.
But if the fuel mixture leaves this chamber unburnt, it might combust in the exhaust system and create a backfire. This backfire can severely damage the entire exhaust system, so it is not something to ignore.
12. Poor fuel economy

As incomplete combustion leaves the extra fuel unburnt, you might experience poor fuel economy. It’s another symptom of bad ignition coils. When they cannot provide enough voltage to the spark plugs, the fuel will not be converted into a usable mixture.
As a result, the fuel consumption might be higher with a broken ignition coil than it was before this part failed. In the long term, your budget will be affected by the increased fuel costs, and you will also have to refuel more often.