Ignition Coil Information
Table of Contents
- What is an ignition coil?
- 5 symptoms of a bad ignition coil
- 1. Check Engine Light (CEL):
- 2. Drop in fuel efficiency:
- 3. Engine misfires:
- 4. False starts:
- 5. Vehicle stalling:
- How long can you drive before you replace ignition coils?
- Ignition Coil FAQs
What is an ignition coil?
Ignition coils are dual-coiled electrical inductors that increase voltage coming from your battery. In some vehicles, this power is then split up by your distributor and sent out to your spark plugs to fire your engine pistons. Other designs have their coils mounted directly to the spark plugs. Coils provide enough electricity to generate the sparks needed to fire you cylinders. This function makes them necessary for your vehicle to operate.
Your vehicle's ignition system relies heavily on the ignition coil.
This electrical transformer plays a crucial role by converting your battery's low voltage into thousands of volts needed to create an electric spark in the combustion chamber.
It's this spark that ignites the air-fuel mixture within, allowing for efficient engine operation and optimal vehicle performance.
In distributor-based ignition systems, this increased power goes out to your distributor, and eventually to your spark plugs. In other designs, there are several smaller coils that service individual cylinders or pairs of cylinders. Either way, the purpose is to light up the fuel in your combustion chambers, moving your pistons and powering your vehicle.
A bad or faulty ignition coil can lead to issues like poor fuel economy, backfiring from the exhaust system, and even engine misfires.
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Types of ignition coils & differences
Coil-Near-Plug (CNP) | Coil-On-Plug (COP) | Stick Coil |
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A coil-near-plug system, as implied by its name, is located near the spark plugs within an engine. | The coil-on-plug system, conversely, places each individual single coil directly onto each spark plug eliminating need for plug wires altogether. | The last variant, the Stick Coil, is commonly used in motorcycles but also found in some car models. |
The main difference of CNP coils is that they often use short plug wires for connection which can reduce potential electrical interference. | The difference in this design is that it enhances overall performance while reducing chances of faulty connections or bad sparks due to wire issues. | The difference of this coil is the compact unit integrates both primary and secondary windings into one long tube that fits inside the valve cover overtop the spark plug. |
5 symptoms of a bad ignition coil
A bad ignition coil can manifest in several ways.
1. Check Engine Light (CEL):
Your vehicle's check engine light may illuminate, signaling potential issues within the electrical system.
When a bad ignition coil malfunctions, it sends a trouble code to your vehicles CPU, depending on what the issue is, the diagnostic code may vary from issue to issue.
2. Drop in fuel efficiency:
Poor fuel economy is another sign, as faulty coils disrupt the air-fuel mixture in your combustion chamber leading to inefficient burning and increased fuel consumption.
3. Engine misfires:
Most vehicles have one ignition coil per cylinder or one coil per two cylinders (in a wasted spark system).
A failing ignition coil can also cause your combustion cylinder to fire incorrectly, which will often lead to an engine misfire in the cylinder where the faulty ignition coil sits.
For example, a 4-Cylinder car may be misfiring in one of the four cylinders, meaning one or all the ignition coils representing those cylinders needs to be replaced.
These misfires often occur when trying to accelerate, or sitting at idle after a cold start.
4. False starts:
If starting up your car becomes an ordeal, it could be indicative of a bad spark plug linked with a malfunctioning secondary coil.
With a failing ignition coil, it's not able to deliver the full voltage to the spark plugs to start the engine properly.
These irregular sparks are not enough to start your engine properly, and often leads to false starts when it's time to get on the road.
5. Vehicle stalling:
Last but not least, frequent stalling while driving is often symptomatic of significant problems within the ignition system including potentially defective primary or secondary coils causing overall engine misfire.
How long can you drive before you replace ignition coils?
There isn't a set schedule for replacing ignition coils, and many vehicle make and models will vary in ignition coil replacement intervals.
The need largely depends on various factors such as the conditions in which you drive and signs of wear-and-tear like consistent engine misfires or recurring check engine light warnings.
On average most newer cars can go for 80,000 - 100,000 miles before needing replacement coils.
Keep in mind any performance modifications to your vehicles engine that increases power substantially will have an effect on your ignition coils and often require you to replace both your coil packs and spark plugs all together.
Ignition Coil FAQs
Can I drive with a bad ignition coil?
You may be able to drive with a broken ignition coil, though we don't recommend it. In our experience, driving with a bad ignition coil has a greater chance of damaging other parts of your ignition and emission systems, such as fouling spark plugs, ruining oxygen sensors, and damaging your catalytic converter.
Can I replace just one single ignition coil?
Depending on your vehicles issue, it is possible to only replace one coil at a time. If it's only one faulty ignition coil causing your cars misfires, it's totally fine to only replace the single faulty coil instead all at the same time.
Should I replace spark plugs with my ignition coils?
If your ignition coils have failed due to bad spark plugs, it would be wise to replace both parts at the same time. Replacing a bad ignition coil without replacing a worn out spark plug would likely result in the same fate since a worn out spark plug requires your ignition coil to work much harder on its own.
What kills an ignition coil?
Ignition coils die for many reasons, the most prominent being the parts location. Coil packs usually sit on top of spark plugs near your engines valve cover. This location tends to be exposed to dirt and oil, extreme heat, and mass vibrations which wear on your coils over time.
Written By:Edson Farnell | Email | 
