7 Symptoms of a Bad Ignition Coil ( and Replacement Cost )

Ignition coil service

When it comes to your vehicle, there are numerous things that can potentially go wrong – and to this end, being aware of some of the most common and easily recognizable symptoms of a bad ignition coil can be hugely helpful.

But what is an ignition coil, why is it important that your vehicle’s ignition coil is working effectively, and crucially – how can you recognize when the ignition coil is not at its best?

What is Ignition Coil?

First things first, we need to answer: what is an ignition coil? Indeed, ignition coils are hugely important components in your vehicle, but if you’re not already a vehicle expert, you may have only heard of them in passing.

Ignition coils, as the name would suggest, play a pivotal role in igniting the fuel for your car, without which the car would be unable to run.

Sometimes, ignition coils are otherwise known as spark coils (for the spark it creates to begin the car running smoothly).

Why is Ignition Coil Important?

Why is the ignition coil important? Of course, without a fully functional ignition coil, you will find that your car struggles to start at all. 

However, even if the ignition coil is only partially worn, you can still face problems such as the car being slow to start and the like.

Why risk it? Make the right choice and give your car’s ignition coil the TLC it needs to continue doing its job effectively and safely instead!

7 Common Symptoms of Bad Ignition Coil

So, we’ve clarified that ignition coils are crucial for starting your car. But how can you tell when something might be going wrong with your car’s ignition coil? Well, there are a few notable symptoms you should be aware of.

This is something that’s true both for new and used vehicles. Indeed, as Motorborne explains, your car could have faults that you don’t quite realise, so always be cautious when it comes to checking everything is working as it should.

We’ve outlined some of the 7 most prominent symptoms of a bad ignition coil as follows. Hopefully, this will help you keep your car running smoothly. 

And remember – if you ever need further advice on your ignition coil, contact your local mechanic. Replacing an ignition coil usually costs a couple of hundred dollars, so it’s better to be safe than sorry.

1. The engine light is coming on.

One of the first signs of a bad ignition coil that you might recognise in your vehicle is that the engine light is coming on. This handy little light on the dashboard of your car may not give you much information about what the problem is with your vehicle’s engine. 

Nonetheless, it will help you understand that there is some sort of problem going on that you should really get checked out. It is possible that the problem with your vehicle’s engine could be due to a faulty ignition coil. 

You should especially suspect this if you notice some of the other symptoms from this list, too.

If you use a car diagnostic tool, you may see the engine code P0351. This represents a primary or secondary circuit malfunction in your ignition coil.

2. Engine is backfiring or misfiring

Have you ever noticed that your vehicle’s engine is misfiring or backfiring? Unsurprisingly, no vehicle is designed to do this, and so this is a big warning sign that something is up.

Engine misfiring is actually the result of unburned fuel being present in the combustion cylinder and can do a huge amount of damage to the exhaust system. 

Of course, a faulty ignition coil could be one cause for this, so make sure you get this checked out as soon as possible.

3. Noises from the engine

Have you noticed that your engine appears to be making strange noises or is otherwise particularly loud? 

A bad ignition coil could be the cause of this, and this causes the engine to work in overtime to try and keep the car running.

4. Vehicle not accelerating efficiently

Have you noticed recently that your car seems “reluctant” to accelerate? Or maybe you’ve seen that your vehicle just seems to lack its normal oomph and power? 

If this is the case for you, then you may want to get the ignition coil checked out by your local mechanic before the problem develops into a more serious one down the line.

5. Low Fuel Efficiency

None of us like having to spend more when it comes to fuel than we need to, but if your vehicle’s ignition coil has gone faulty, you might find that you have much lower fuel efficiency than you expected. This can leave you forking out more for fuel than you should need to, so get this checked out.

6. Vehicle stalling

It’s easy to put off your vehicle stalling as the “car being a bad model” or your own driving skills being the issue. However, if you notice that your car is regularly stalling for no apparent reason while you’re driving along, this most likely isn’t the result of your own driving skills – especially if the car used to drive fine. 

Instead, it’s possible that your ignition coil has developed a fault, due to the coil not delivering stable current to the spark plug.

7. Car won’t start

The ignition coil is responsible for starting your car. Indeed, it provides the power to the spark plug to then ignite the fuel and get the car running. So, as a final symptom, if your car doesn’t start at all (or has begun struggling to start) you’ve likely got a fault going on.

Of course, once you get to this point, you may be unable to go anywhere, so try and look out for the six other signs before you find yourself stranded at this point.

Cost to Replace your Ignition Coil

Usually, if you need to replace your ignition coil, you can expect to pay around $150-$200 at a regular automotive service station. However, if you take your car to a specialized auto body shop, the cost of this service is much lower – around $75-$100. 

While the price to have your ignition coil will vary depending on where you wish to have it replaced, anywhere from $50 to $300 is considered reasonable for an ignition coil change.


Keeping your car in top working order doesn’t need to be impossible. All the same, by checking your ignition coil regularly and keeping an eye out for these 7 common symptoms of a bad ignition coil, you’ll hopefully offset the onset of problems arising with your vehicle.

Don’t compromise on your vehicle’s safety and don’t leave things to chance; replacing the ignition coil isn’t a massive expense, so make the right decision for your car and invest in a new ignition coil if you notice any of these symptoms!