Can a Bad Coil Pack Cause Rough Idle? (Quick Answers)

A coil pack is essential in any vehicle. It helps to start the engine in the vehicle so that you can drive your car. It can also be found in various other forms and names in different machines and electronics.

Coil packs can become worse and cause problems in the engine. You may ask if a bad coil pack causes rough idle. Let us help you find the answer you are trying to find and provide you with some essential information regarding this matter.

Can a bad coil pack cause rough idle?

A bad coil pack can cause rough idle. It causes the engine not to run smoothly and may cause irregulates in the speed of the engine. Therefore, you may feel that the engine is speeding up and down while idling. Due to this, your engine will not run smoothly as it should be.

A coil pack can go bad at any time. This can cause various issues in the engine while it is running. Among all of those issues, rough idle is the most common of all. Rough idle is bad for any engine of a vehicle.

A rough idle means that the engine may not run at its expected rate of operation. You will find that the engine is suddenly losing and gaining RPMs without any prior input to the engine by the driver. Your vehicle engine may even all below the optimal running rate as well.

It is common to see that the engine’s rpm jumps down to 600 rpm sometimes. But this may drop more depending on the model of the vehicle. As a result, you will find that vehicle is not running smoothly and is causing vibrations and frequent speed jumps and drops.

Another major issue that it causes is the engine will not reach its optimal temperature. A coil pack is essential to warm the engine to start. It causes ignition in the engine and helps to start the engine. But if the coil pack is being bad, the engine will not start.

There are many more issues that a bad coil pack can cause. Such as backfire in the vehicle, poor mileage, and many more. If you face one or multiple of them, you can say that a bad ignition coil causes rough idle.

How does a bad ignition coil pack cause rough idle?

A bad ignition coil causes a lot of problems. Among all those problems, rough idle is one of the biggest. Rough idle causes the engine not to run smoothly. While driving your vehicle, you will want your vehicle to run smoothly.

You will often keep the engine idling in the signal or in any other case as well. You may sometimes find that the engine is not running smoothly during that time. The speed is jumping up and down while the engine is idling.

Speed jumping means that the engine is rapidly changing its rpm which is a common occurrence due to a bad ignition coil pack. This is also called rough idle. You may find your engine speeding up and down as low as 600 RPMs. 

The rpm change will vary based on your vehicle model.

What are the symptoms of a bad ignition coil pack?

There are multiple symptoms of a bad ignition coil pack. If you want to know some of them, here are some noteworthy symptoms of a bad ignition coil pack that we think you should know:

Rough idle in the vehicle:

Rough idle is the most common thing in any vehicle due to a bad ignition coil pack. This causes the engine to speed up and down without any warning. This can cause the engine to shut down as well if the rpm of the engine drops down below the limit. 

Therefore, the engine will not run smoothly.

Engine check light turn on:

A bad ignition coil pack means that a part of the engine is not properly working. When any part of the engine is not properly working, this can cause the engine check light to turn on. 

This means that the engine is not properly functioning and needs maintenance. This is another symptom of this issue.

Backfire and misfire in the vehicle:

A bad ignition coil pack can cause a backfire and misfire in the vehicle. Backfire means that the engine will blow out fuel from the exhaust pipes and misfire means that the engine will overheat and cause sparks. 

These are all not good for any engines and all indicate that there is a problem in the ignition coil pack.

Poor fuel economy while using the vehicle:

Due to a bad ignition coil pack, you may find your fuel economy way below than usual. This means that you will need more fuel than your usual requirement to reach the same distance.

Issues in starting the engine:

This is another major symptom of a bad ignition coil. If the coil is bad, the engine will not receive enough sparks in the chamber. Therefore, you may not start your vehicle without trying multiple times to start or by changing the coil pack.

How to test coil pack without multimeter?

Testing coil pack with a multimeter is a common way to check this part of your vehicle. But if you want to test it without a multimeter, it is possible. Here are the steps that you will have to follow in order to test coil pack without multimeter:

Locate the position of the coil pack:

Before doing anything, wear all necessary safety equipment. Turn off the engine and open the hood of the engine block. Although the location of the coil pack will vary depending on the model of the vehicle, you may find it near the fender or distributor.

Observe if any misfire occurs:

Check which cylinder is causing a misfire in the engine one by one. If any of the coils in any cylinder is causing a misfire, mark it to swap it with another coil of another cylinder of the engine.

Swap the coils of the other cylinders and check again:

Swap the coil of the cylinder that is causing a misfire with a good cylinder. If the coil is still causing a misfire in the replaced cylinder, it means that the coil is faulty and needs to be replaced.

How long can I drive my car with a bad ignition coil?

Depending on the severity of the ignition coil, you can drive your car until it breaks down completely. Although a bad ignition coil does not completely break down a car, it can cause a lot of harm if you do not fix this issue as soon as possible. 

A bad ignition coil can cause many issues, but it does not cause any major issues to drive a car. But if you keep driving the car with the problem, the engine may catch fire or worse.

How much does cost to fix bad ignition coil?

Depending on the model of your vehicle, it may cost you around 70$ – 350$. An ignition coil costs around just 60$ – 80$ depending on the model of the vehicle. But the installation cost of it is higher than expected. 

Depending on your location, it can cause around 20$ to 300$ for installing it by a car mechanic.

What can cause a rough idle in a car?

There are multiple things that can cause a rough idle in a car. Here are some common causes behind a rough idle in a car:

Bad coil pack:

A bad coil pack is the most common reason behind a rough idle in a car. Due to this, your car may not run smoothly as it did before. You may also face issues while trying to start the vehicle. 

But due to this, your engine will speed up and down while idling, which is the primary outcome of a rough idle in a car.

Dirty or bad spark plugs:

Sparks plugs are another reason behind a rough idle in a car. If the sparks plugs are dirty, this may cause the engine not to create enough spark to start the engine. Therefore, you will have to perform multiple attempts to start the engine. 

You may also find that the engine is not running smoothly during idling.

Blocked fuel injectors:

Fuel injectors are essential for any car. It helps the vehicle receive the necessary amount of fuel to run properly. But if they are blocked due to dirt or bad due to aging, this may cause the engine to face rough idle.

Final thoughts

A bad coil pack can cause the engine to face rough idle. This may cause the engine to run smoothly as it was intended to. It may also cause the engine to mourn from poor fuel economy, hard to start the engine, and many more. Therefore, this may cause a lot of problems to a car.