bad coil pack symptoms

Bad Coil Pack Symptoms: Everything You Need To Know

Ignition coils are super important for your car’s Engine because they make the electricity that starts the fuel burning in the cylinders. If you notice signs that the coil pack might be broken, it could cause significant problems for your car.

This article will give you details about the bad coil pack symptoms and how they can damage your vehicle. We’ll talk about rough idling, using too much gas, misfires, and insufficient needing more power. So, learn to figure out if your coil pack is terrible and what to do about it before you get stuck at a terrible time.

How Does an Ignition Coil Work?

The ignition coil is a crucial part of your car’s ignition system. It takes the 12-volt power from the vehicle’s electrical system. It transforms it into a high-voltage current necessary to ignite the fuel in the cylinder. This spark is what starts the Engine and keeps it running smoothly.

The ignition coil acts as an electrical transformer, increasing the voltage from the battery to create a powerful spark. The spark moves from the ignition coil to the plugs through the wires. It set off the air-fuel mix in the engine cylinders. Your car won’t start or run right if the ignition coil isn’t working. The ignition system has many parts that work together to start the engine smoothly and keep it running. The most crucial components of this system are:

Spark plug

The spark plug is a crucial part of your car’s Engine. It creates sparks that ignite the fuel-air mixture, leading to combustion. This explosion generates energy that pushes the pistons down, setting off a chain reaction that ultimately turns the crankshaft and powers your car.

Your Engine needs a suitable spark plug to make sparks for burning fuel. If the spark plug is not working well, your Engine won’t work well either. This can cause problems and might even damage your Engine. To keep your vehicle running smoothly and using fuel efficiently, it’s essential to check and change the spark plugs regularly as part of your maintenance routine.

Ignition distributor

bad coil pack symptoms

The ignition distributor is a crucial part of the car’s ignition system. It controls the timing of the spark that ignites the fuel in the Engine. In the distributor, there’s a part that makes sure the spark happens at the right time. When it’s time for the spark, the car’s computer sends a signal to the distributor through a wire. This tells the distributor to make the spark plug work at just the right moment. This process is essential for ensuring that the Engine runs smoothly and efficiently.

Bad Coil Pack Symptoms

Ignition coils can be affected by a range of issues including but not limited to:

  • Engine performance suffers due to backfiring
  • Engine stalls, particularly at idle
  • Check Engine Soon light is illuminated

What Is Backfiring?

Backfiring is a loud noise that sounds like a gunshot and can happen in a car engine. Issues with the spark plug, ignition coil, or fuel injector often cause it. The most common reason for backfiring is when the spark plug fires before the piston reaches the top dead center (TDC) on its compression stroke.

This premature ignition causes unburned fuel to ignite, leading to backfiring. Excess fuel entering the cylinder during the intake stroke can also cause unburned fuel to come through the exhaust system. If your car’s Engine is backfiring, it could indicate problems with the spark plugs, ignition system, or fuel injection.

What Does It Mean When Your Engine Is Hard To Start?

If your car is tough to start, it might be because of several problems. A bad coil pack is a common reason, making it hard to start your vehicle and causing it to run rough. Another possible issue could be old spark plugs, wildly if they are misfiring. This can make it challenging to start your car and cause problems when idling.

It’s also worth checking for dirty or faulty fuel injectors, which can contribute to hard starting and decreased gas mileage. If you’ve recently installed new spark plugs and are still experiencing difficulties starting your Engine, the issue lies with the fuel injectors. Keep an eye out for any drop in fuel economy as well, as this could indicate a problem with the fuel system.

Signs Of A Poor Fuel Economy

bad coil pack symptoms

There could be various reasons why your fuel economy needs to meet your expectations. One potential cause is a faulty ignition coil in your vehicle. If this turns out to be the issue, you might observe some of the following signs:

  • No acceleration when starting from a stop
  • Reduced overall power
  • Engine misfires

Vehicle Stalling

It could indicate a bad ignition coil if your vehicle is stalling. Stalling can be caused by several factors, and it’s important not to ignore this symptom as it can be dangerous. You may have trouble accelerating or changing gears appropriately when your car stalls. It could lead to an accident if another driver rear-ends you. Faulty ignition coils may require more frequent replacement, making them more expensive in the long run.

Check Engine Soon Light

bad coil pack symptoms

The check engine light is another sign that something’s not quite right here. It’s not a specific diagnosis but more of a heads-up that there could be an issue with your vehicle. When you see this light come on, you must take your car to a mechanic for further inspection. They’ll use diagnostic tools to determine what’s causing the light to come on and recommend the necessary repairs.

  • The check engine soon light can be triggered by various problems, such as:
  • A faulty ignition coil
  • A malfunctioning O2 sensor
  • Low fuel pressure in the fuel rail

Average Ignition Coil Replacement Cost

The average cost of replacing an ignition coil in your car can range from $168 to $218 for the replacement parts. If you need a professional to replace you, the average labor cost is between $51 and $64. Ignition coils are crucial for creating the spark that fires up your Engine, and they can fail due to age or physical damage. If you notice signs that your ignition coil is failing, it’s crucial to replace it promptly to avoid further issues.

It’s essential to watch for symptoms such as rough idling, poor fuel economy, or difficulty starting the Engine, as these could indicate a failing ignition coil. You can prevent more severe problems by addressing the issue early and getting a timely replacement; you can avoid more severe problems.

When To Get A Vehicle Check

If you notice any of these signs, like a check engine light turning on, poor gas mileage, or your car stalling, it might be time to check your vehicle’s ignition coils. Ignition coils are crucial for your Engine’s performance, and if they fail, it can lead to various problems. It’s best to have them replaced by a professional as soon as possible to avoid further issues with your vehicle. Ignoring these signs can lead to more severe problems, so it’s essential to address them promptly.


Awareness of bad coil pack symptoms is crucial for maintaining the optimal performance of your vehicle. Recognizing signs such as rough idling, engine misfires, and loss of power, you can address potential issues before they escalate. Regular maintenance and timely replacements can prevent costly repairs down the line. Remember that a well-functioning coil pack is essential for efficient fuel combustion and overall engine performance. So, if you notice any of these symptoms in your car, don’t hesitate to get it checked by a professional mechanic to keep it running smoothly for years.


Can I drive with a bad coil pack?

It’s not recommended to drive with a bad coil pack as it can lead to further damage to the Engine and a decrease in performance.

How do I diagnose a bad coil pack?

 You can diagnose a bad coil pack by using an OBD scanner to check for error codes related to misfires or by visually inspecting for signs of damage or wear.

Can a bad coil pack cause the check engine light to come on?

 Yes, a bad coil pack can cause the check engine light to come on, especially if it leads to misfires or other issues affecting engine performance.