A coil pack, simply put, is an electronically controlled pack of ignition coils regulated by the car’s computer. The coil pack within your car is an important piece of the ignition system. Without the coil pack properly functioning, the ignition system won’t work, and your car won’t start.
Although numerous parts of your car are imperative and must work together in order to function at an optimal level, the coil pack may be one of the most important components in starting your car and engine.
Once the coil pack fails, engine misfiring can happen because one or more spark plugs in the engine cylinders didn’t receive enough voltage. Replacing a coil pack consists of fixing the ignition coil. The average price of fixing the ignition coil is between $264-$376.
What Is A Coil Pack?
A coil pack is an electronic piece of equipment within the ignition system. This electronically-controlled pack consists of ignition coils that are controlled by the car’s main computer.
The main job of the coil pack is to increase and build the energy needed, and then release the voltage through the spark plug cables. When the energy reaches the spark plugs, it starts the combustion process.
In more modern cars today, the distributor is replaced by the coil pack. This is typically because the coil pack is more reliable and consistent than the distributor. In addition, the coil pack provides a better spark, which causes more efficient and quicker combustion, along with higher horsepower.
Coil Packs: A Quick History
In the mid-80s, distributors began to disappear, replaced by coil packs that fired pairs of “companion” cylinders (those are the cylinders on four-stroke engines where the two companion pistons always reach TDC at the same time).
In other words, coil packs fire virtually every time each piston reaches the top of its stroke, but most of the energy is expended in the firing cylinder. This kind of ignition is also referred to as “waste spark” because even during the exhaust stroke, the spark plug fires.
Motorcycles have used this kind of ignition for literally decades, but there are still primary and secondary windings in the coil pack, which receives voltage with the key on and the ground pulse from an ignition module or the ECM/PCM.
What Is An Ignition Coil?
As we said, the ignition coils make up the bigger coil pack. An ignition coil is an induction coil in a car’s ignition system. An induction coil is a spark coil that produces a high voltage from a low voltage supply.
The job of the ignition coil is to transform the battery’s lower voltage to a much higher voltage that is needed to create the electric spark in the spark plugs. The spark created will then, in turn, ignite the fuel.
The electric spark generated due to the high voltage is a quick electric discharge that occurs as a result of an ionized and electrically-conductive channel. The electric spark occurs in the spark plugs.
The spark plugs are devices for delivering the electrical current from the ignition system to the combustion chamber of the engine.
They will then be able to light the compressed fuel and air mixture by the electrical spark created, while simultaneously keeping the correct level of combustion pressure in the engine. A common cause of the ignition coil failing is due to a spark plug gap.
Energy Process Of Ignition Coil
The ignition coil consists of an iron core surrounded by two coils of copper wire. The ignition coil contains a magnetic circuit, meaning the iron core doesn’t form a closed loop. The energy kept in the magnetic field of the core is the energy transferred to the plug.
Within cars, smaller coils are used with one coil for each spark plug. A larger ignition coil can produce about 40 kV. These coils can be mounted on top of the spark plug, and are called a direct ignition plug. Coils can also serve two spark plugs, and are called the wasted spark system.
The wasted spark system consists of one coil generating two sparks per cycle to each cylinder. The fuel within the cylinder can then be ignited. The wasted spark system is more reliable than a single-coil system, and is also less expensive than a coil-on-plug option.
Types of Ignition Coils
Generally, there are three different types of ignition coils used on vehicles. They include:
- Traditional ignition coils – Commonly found in older cars, these coils are attached to the distributor and use wires to connect to the spark plugs. When they fail, you typically experience hard starting, rough idling, backfiring, misfiring, or decreased fuel efficiency across all cylinders.
- Coil-on-plug (COP) – Common in newer vehicles, these coils are placed directly over each spark plug, eliminating the need for separate spark plug wires. Since each cylinder has its coil, a faulty coil can cause issues in just one cylinder, making diagnosis easier.
- Distributorless ignition system (DIS) – Uses one coil or a set of coils to ignite multiple spark plugs, eliminating the need for a distributor. Since the DIS controls multiple spark plugs, a single faulty coil can affect multiple cylinders, but not all of them.
How To Tell If An Ignition Coil Is Bad?
If you’re having an issue with the coils, you can usually tell by a few signs and symptoms that there’s something wrong. There are a few key steps you should take to determine if the problem is going on with your ignition coil, coil pack, or another part of your car.
First, you should test the coils with a multimeter. Ignition coils retrieve energy from the battery, which is usually at least 12 volts. The coils then convert the energy to a higher voltage, of atleast 50,000 volts, in order to create a spark.
This energy then travels via the distributor to the spark plugs, and then ignites the fuel. Some vehicles only have a couple of ignition coils that can power various spark plugs – remember the wasted spark system we were discussing earlier. Other models use one ignition coil per plug.
The number of coils is irrelevant to this next step – you need to remove all of your coils, no matter the amount you have. Before you start, make sure you have a multimeter and tool kit.
8 Signs of a Faulty Ignition Coil
Here are the symptoms you need to look for as the signs of a bad ignition coil.
Your Car Guzzles Gas
Ignition coil problems could be why you must stop at the gas station more often than usual, even if you are not putting more miles on the clock. When a battery doesn’t send enough power to the spark plugs, your car compensates by burning more gas.
Your Car Feels Slow
It could be a bad ignition coil when you step on the gas pedal, and your car is slow to respond and feels lazy. The fuel-air mixture is not igniting correctly, causing your vehicle to lose power.
You Hear Spluttering, Coughing, and Banging Noises
If your car makes spluttering and coughing sounds, blame a bad ignition coil. The sounds are from a cylinder that’s not firing correctly or not at all during the ignition process. If you hear loud banging noises, it’s from exploding unused gas in the combustion cylinders.
Your Car Idles Roughly and Vibrates
A problem with the ignition coil will cause your car to idle roughly and vibrate. A malfunctioning coil can’t supply the voltage required to create consistent sparks, causing your car to jerk forward when you step on the accelerator.
Your Car Misfires and Backfires
Ignition coils help ignite the engine’s air-fuel mixture, and a problem can cause a misfire. When your car backfires, it means one of the cylinders isn’t firing correctly or not at all. This could damage the catalytic converter and other engine components. You may even see smoke pouring out of your tailpipe and smell gas.
Your Car Stalls
A bad ignition coil doesn’t deliver the necessary voltage to the spark plugs, making it difficult to start the engine. Your car will stall when you stop or die without warning.
You Struggle to Start Your Car
Most modern engines have one ignition coil per cylinder, while older cars use a single coil. If the coil fails, it will not deliver the correct voltage to the spark plugs. Your vehicle will crank but not start.
The Check Engine Light Is On
Hard starts, backfires, and misfiring will trigger the check engine light. Never ignore the check engine light on your dashboard and get repairs as soon as possible to avoid more damage that will lead to higher repair costs.
How to check ignition coil?
To test an ignition coil, you’ll need the following tools:
- Multimeter for measuring the resistance of the ignition coil.
- Spark tester to check for a strong spark.
- Basic hand tools such as screwdrivers and socket wrenches.
- Owner’s manual to locate the ignition coils and confirm the specifications for testing.
For more precise diagnostics, consider using:
- An oscilloscope that provides a detailed analysis of the ignition coil’s voltage output.
- OBD-II scanner to help identify trouble codes related to ignition system failures.
Step-by-Step Guide to Testing Your Ignition Coil
Step 1: Perform a Visual Inspection
Start by visually inspecting the ignition coil for any signs of damage. Look for cracks, burn marks, corrosion, or melted plastic on the coil housing. Damaged wiring or connectors can also cause coil failure. If you notice visible damage, the ignition coil must be replaced.
Step 2: Test Resistance
A multimeter lets you measure the resistance in the ignition coil’s primary and secondary windings.
- Turn off the engine, disconnect the battery, and remove the ignition coil from its mount.
- Set your multimeter to ohms (Ω). Place the positive and negative probes on the ignition coil’s primary terminals. A typical reading should range between 0.4 and 2 ohms, depending on the vehicle.
- Place one probe on the positive terminal and the other on the output terminal (where the spark plug connects). A healthy coil should read between 6,000 and 10,000 ohms.
If the resistance is outside the specified range, the ignition coil is faulty and should be replaced.
Step 3: Check for Spark
If the multimeter readings are within range but you still suspect an issue, use a spark tester to check for a strong spark.
- Reinstall the ignition coil and connect the spark tester to the coil and a grounded part of the engine.
- Start the engine or crank it. Watch the spark tester’s gap for a strong, blue spark.
- If no spark or a weak spark is visible, the ignition coil is likely faulty and needs replacement.
What to Do After Testing Your Ignition Coil
If the resistance readings or spark test indicate a problem, the ignition coil needs to be replaced. If everything checks out but symptoms persist, the issue may lie with another component such as the spark plugs, ignition control module, or wiring.
There’s no set interval for replacing coils, and you can usually expect them to last more than 100,000 miles. Ignition coils can wear out over time, though, particularly if other parts like spark plugs are not maintained. Always use high-quality replacement parts to ensure reliability and longevity.
Knowing how to test a spark plug coil is beneficial for diagnosing ignition issues and keeping your car running at its best.
Average Cost of Ignition Coil Replacement
The ignition coil replacement cost can vary significantly depending on the type of vehicle and the ignition coil used. For standard vehicles with conventional ignition coils, replacing a single ignition coil can range from $100 to $300.
However, for vehicles equipped with more advanced ignition systems like coil-on-plug (COP) or distributorless ignition system (DIS) coils, the cost may be higher, ranging from $200 to $600 per coil.
The total cost of ignition coil replacement consists of two main components: the cost of the ignition coil itself and the labor charges for installation. Ignition coils can vary in price based on their type and quality, ranging from $50 to $200 or more for each coil.
Labor costs for ignition coil replacement are typically charged per hour of work. On average, labor rates can range from $50 to $150 per hour, depending on the location and the repair shop.
The labor time required for ignition coil replacement can vary from 0.5 to 2 hours, depending on the vehicle’s design and the number of coils needing replacement.
For example, the total cost of replacing a single ignition coil in a standard vehicle with a conventional ignition system could be around $150 to $350, including the cost of the coil and labor charges. For a vehicle with a more advanced ignition system requiring a higher-priced coil and more labor time, the total cost could be $300 to $800 or more.