Ignition Coil Replacement (Cost & Steps)

Are you suspecting that your ignition coil is faulty and you need an ignition coil replacement but don’t know how to go about it? If so, Worry no more because you’re on the right page.

This article will explain everything you need to know, about an ignition coil replacement, how much an ignition coil replacement costs, how to perform an ignition coil replacement yourself, how to choose the right mechanic for your ignition coil replacement, and lots more.

Let’s begin!

How to Replace an Ignition Coil

Ignition Coil Replacement

Your engine’s ignition coils generate electrical currents from the ignition wires (spark plug cables) to your spark plug. The generated current then passes through the spark plug and detonates your cylinder’s fuel and air mixture.

A malfunctioning ignition coil may cause an engine to misfire or make the engine unable to run. When you have determined which ignition coil is the source of the issue, your ignition coil can then be tested to verify that it is a problem.

You can replace a faulty coil in a couple of hours with simple hand tools. The replacement of an ignition coil involves three main steps;

  1. Old Coil disconnection
  2. New Coil swapping
  3. New Ignition Coil connection

Also Read: Bad Ignition Coil Symptoms (Causes and Solutions)

Phase 1: Disconnecting the Old Coil

1. Disconnect the Negative Terminal on Your Battery

Your battery can either be in the engine or the vehicle’s trunk. It resembles a rectangular-shaped box, with two terminals (posts) protruding from its top.

A plus (+) sign label will be used to identify the positive post of the terminals, and a minus (-) sign will identify the negative post. An appropriately sized socket, or wrench and ratchet, should be used to untighten the bolt that secures the negative terminal to the cable. After it is unscrewed, slide the bolt off.

To prevent the cable from unintentionally touching the battery terminal again while you are working, tuck it down beside the battery.

You need to disconnect the power while the coil is being replaced to ensure that you don’t get shocked and the vehicle’s electrical system doesn’t get damaged.

Avoid touching the negative and positive terminals simultaneously with the wrench to avoid an electric shock.

2. Locate the Ignition Coil That Needs to Be Replaced

Depending on your vehicle, you could have only one ignition coil that has outlets for each of the cylinders, or each cylinder could have its coil. Suppose you’ve determined which exact ignition coil has to be changed with an OBD-II code scanner.

In that case, an application-specific repair manual can help you identify the specific coil responsible for the detected error code that your scanner reported.

However, if the faulty coil was identified with an ignition spark tester, you will already know which exact coil needs to be removed.

3. Label the Cables Running Into the Coil if There Is More Than One

If your vehicle’s ignition coil supplies current to more than one cylinder, number them using a marker to remember their connection sequence. Number each ignition wire connected to your ignition coil, from left to right, to connect the cables to the replacement coil similarly.

If the ignition cables connected to your coil are arranged in two rows, start the numbering from the top left to the top right, then number the second row similarly.

You could use a permanent marker to do this if you have grey cables. However, if they are black, a paint pen can be used to ensure that the numbers are legible.

4. Disconnect Each Cable Leading Into the Coil

Your ignition cables should be gripped as close as possible to the ignition coil itself. Squeeze firmly, then pull your cable’s boot (your cable’s connector portion) off your ignition coil. It may be necessary to pull and squeeze hard to disconnect each cable.

If just one cable goes to the ignition coil, only that cable would need to be disconnected.

Don’t pull on your ignition cables in any place but low on your boot; otherwise, the cable’s internal wiring could be damaged.

5. Tuck the Ignition Cables to the Side

After disconnecting your ignition wire or wires from the ignition coil, the cables might hang and hinder access to the ignition coil. Instead, simply tuck the cables behind the ignition coil or others nearby to easily access the coil.

You don’t need to be concerned about mixing the cables up because they are all numbered.

6. Release the Clip on the Plug Running Into the Side of the Coil

One electrical plug goes into the side of your ignition coil. Depending on your coil’s design, the electrical plug may be smaller or larger, but the process of detaching it is typically the same.

To disconnect the plug from the coil, pull it backward after pressing down the plastic clip on it.

Sometimes, you may have to pry the release up using a flathead screwdriver instead of using your thumb to press it down.

If you can’t easily determine how the connection can be released, consult the car manufacturer’s website or an application-specific repair manual for further assistance.

Ignition Coil Replacement

Phase 2: Swapping in the New Coil

1. Unscrew the Bolts Holding the Coil in Place Using a Wrench

An ignition coil may be screwed on using a range of one to four bolts in most applications, depending on your ignition coil’s size. Locate each of the bolts securing the ignition coil, then use an appropriately sized socket and ratchet to unscrew these bolts.

Place each bolt in a secure location, so it can be reused with a new coil.

Don’t try to use a wrench or socket that isn’t compatible with the bolt size. If the bolt’s head is stripped off, you’ll be unable to remove the ignition coil.

2. Remove the Coil From the Engine Bay

After removing the bolts from the ignition coil, grasp the coil in one hand, then drag it away from the engine compartment where it had been mounted. If it does not easily come out, check if you overlooked any bolts and unscrew them.

The ignition coil might be slightly stuck on an engine with grime and dirt, but otherwise, it should easily come out.

3. Compare the New Coil to the Old One Before Installing It

Take your new coil out of its box, and place it on a table beside the old one. Ensure that the number of ignition cable ports on both coils is the same, that the old and new connectors are visibly identical, and the bolts on both coils pass through the same places.

If they’re not a perfect match, you must exchange the new coil and purchase the correct one.

It isn’t uncommon to get the wrong part because the parts in a car can change based on when the vehicle was manufactured and its trim package, even though it was listed as the correct vehicle.

It saves a lot of time to compare the parts you purchased before you begin the installation to ensure that the part gotten isn’t the wrong one.

4. Orient the New Coil in the Same Direction as the Old One

Although the ignition coils used in different vehicles are of different shapes, each has only one installation method. The new coil should be set where it should be mounted to ensure that the bolt holes will line up as they did in the original.

The holes for the bolts will not line up if you attempt to put the coil upside down or backward.

If you can’t figure out how to place the ignition coil inside your car, consult an application-specific repair manual for more instructions.

Connecting the New Ignition Coil

1. Connect the Plug to the Side of the Ignition Coil.

When the sound of your release click is heard, insert the spark plug into the appropriate port on your newly purchased ignition coil. If you do not hear a release click, the connector is not pushed all the way in, and the ignition coil might not work.

If this occurs, pull off the connector and check inside to see if there’s any debris or obstruction. Then try once more.

Don’t try to force this connection, or it could be broken.

2. Plug Each Ignition Cable Into the Coil Using the Order Written on Them

If your ignition coil only had a single cable, it should be directly pressed onto your new coil’s wire port until a sound indicates it pops on. If it had multiple cables, begin with the one labeled ‘number 1’, then connect the cable to the left port at the top. Carry on with the other connections in that order.

When a cable is connected properly, you should hear a pop.

To guarantee a solid connection, you might want to dab some dielectric grease onto the cable ports before you connect them.

Dielectric grease can be purchased at your neighborhood auto parts shop.

3. Reconnect the Battery

Reconnect the cable that you previously removed into the battery’s negative (-) terminal. Then, fasten the bolt using an open-ended socket or wrench and ratchet to keep the cable on the battery terminal in place.

Ensure that your positive cable is still in place. Take caution as your negative cable is being connected to your terminal. A spark may be produced.

4. Start the Vehicle to Test the New Coil

To start your engine, insert the key into your ignition and turn it. If your engine doesn’t start at all, it could be that your battery is either dead or not connected. If the engine attempts to start but cannot, inspect the ignition coil’s connections, then try again.

An OBD-II code scanner should be used to resolve any error codes detected on the engine. Then wait for a while as the engine runs to check if your check engine light starts to flash.

An engine misfire is indicated by the check engine light flashing. Check all connections on the new coil, then ignite the engine again.

Also Read: Ignition Coil Packs (Everything to Know)

Symptoms of a Bad Ignition Coil

Ignition Coil Replacement

Although ignition coils typically degrade with time, some factors might hasten this process, such as heat damage and defective spark plugs.

Regardless of the cause of its defect, the following signs usually indicate a faulty ignition coil:

  1. Backfiring
  2. Poor Fuel Economy
  3. Engine Misfiring
  4. Vehicle Stalling
  5. Engine Jerking, Rough Idling, Poor Power
  6. Check Engine Light On / DTC Code
  7. Engine Hard Starting

These signs could happen individually or may occur alongside other signs. Therefore, each of the symptoms mentioned will be discussed below.

1. Backfiring

Backfiring in your vehicle indicates the early-stage symptoms of ignition coil failure. A car backfiring happens when the unused fuel in your engine’s combustion cylinders escapes through the vehicle’s exhaust pipe.

This problem, if left unchecked, can necessitate expensive repairs. Usually, when there is a backfiring issue, the exhaust pipe will emit black smoke. The gasoline smell in the emitted smoke can also indicate a failure of the ignition coil.

2. Poor Fuel Economy

Poor fuel economy is another indication of a bad ignition coil. If your car is getting significantly less mileage than before, this could imply that you have a faulty ignition coil.

3. Engine Misfiring

A vehicle with failed ignition coils will experience engine misfiring. Attempting to ignite such a vehicle’s engine will cause misfiring that would sound like a sputtering, coughing noise.

When your vehicle is moving at high speed, spitting and jerking will be observed in the vehicle’s behavior. A faulty car’s ignition coil will also experience vibration when idling at a stop light or sign.

4.  Vehicle Stalling

A vehicle with a failed ignition coil may also experience stalling. This can happen as a result of irregular sparks that are sent by the bad coil to the car’s spark plugs. Your vehicle may completely shut off when you bring it to a halt, leaving you with the hassle of hoping it will restart.

5. Engine Jerking, Rough idling, Poor Power

Engine jerking, rough idling, and hesitating during acceleration, are other symptoms of a faulty ignition coil. In addition, your vehicle will feel as though it has less power when you are driving.

6. Check Engine Light On / DTC Code

The check engine light will often be turned on in the dash. When you scan your car with a vehicle diagnostic tool, the engine error code P0351 (Ignition Coil – Secondary/Primary Circuit Malfunction) most commonly shows up.

The simplest method to troubleshoot an ignition coil issue is probably to scan for error codes. So, if the check engine light is turned on, use a scan tool or confirm the error code in an auto repair shop.

7. Engine Hard Starting

If your vehicle uses only one ignition coil, a symptom you may experience is difficulty in starting your engine. If the ignition coil is faulty, your engine will crank without sparks in the cylinders. Sometimes, it could start at first but die immediately.

How to Test an Ignition Coil

Ignition Coil Replacement

Some useful tips on running tests on an ignition coil, depending on whether they’re a COP (Coil-On-Plug) or CNP (Coil-Near-Plug), are given below:

CNP Coil Type

To test the ignition coil, your car engine should be turned off, and the hood should be opened. Next, your spark plug cable should be removed or pulled (if your car uses CNP coils).

Usually, these wires run to your spark plug, from your distributor cap. Insulated tools and rubber gloves should be used when these electrical parts are being worked on, or you could get an electric shock.

  1. Next, connect the new plug to your spark plug cable (old or new plug to check for coil sparks). Using insulated pliers, hold the plug onto any metal component of your engine, and ensure that the spark plug’s threaded portion is in contact with the metal.
  2. Remove the fuse connected to your fuel pump, using needle nose pliers or a fuse removal tool to disable it, then prepare to crank your engine. It may be necessary to have another person present, to help you turn the key in your ignition because you’ll be holding down your spark plug with the needle nose pliers.
  3. After cranking the engine, check for any blue sparks that form along the gap in the spark plug. If blue sparks can be seen, the ignition coil isn’t malfunctioning.
  4. If there are no sparks or orange sparks, this indicates that your ignition coil is faulty.
  5. After the test, your spark plug should be disconnected and placed back into its hole. Reconnect your spark plug cables, then return the fuel pump fuse.

COP Coil Type

  1. Start your engine.
  2. Let the engine run at an idle speed.
  3. Unscrew the bolt of the ignition coil labeled as ‘number 1’, then pull the coil up to check how your engine runs.

An indicator that the ignition coil labeled as ‘number 1’ is good is that the engine’s condition will change to rough idling.

You can then repeat this test on all remaining coils in a consecutive manner until the culprit is found. When a malfunctioning ignition coil is pulled out, the engine idle/condition shouldn’t change.

Ignition Coil Problems

An ignition coil failure is common in various cars. The symptoms of a faulty ignition coil are engine misfiring (lack of power), shaking, and sputtering.

The vehicle’s Check Engine Light will flash or remain ON, on your dashboard. In vehicles with one single coil pack or coil, a bad ignition coil (or ignition coil pack) may result in problems in starting the engine.

A car’s ignition coil will more likely fail if the spark plugs have not been changed for a long time. The reason is that the gap between a spark plug’s electrodes increases with age, and a larger gap would cause increased electrical resistance. As a result, your ignition coil will have more strain.

Can You Drive With a Bad Ignition Coil?

The engine often misfires if the ignition coil is bad. In some vehicles, the engine misfire when driving can make the catalytic converter melt due to overheating. Changing the catalytic converter is costly.

A faulty ignition coil has also been known to cause harm to the engine’s computer (PCM). Although some car manufacturers advise that the engine shouldn’t be driven at all if it misfires, others suggest that driving should be done moderately.

The vehicle should be checked out without delay. Consult the car’s owner’s manual for more information.

Ignition Coil Safety Precautions

The ignition coil produces a very high voltage that’s hazardous to your health. When working with the ignition components, the safety precautions in your vehicle’s service manual should be strictly followed.

We’ve posted various links in this article that provide you with subscription-based access to your factory service manual. When you’re replacing or disconnecting ignition coils, the first thing is to detach your negative battery wire.

Ignition Coil Replacement

Ignition Coil Replacement Cost

If you find out that you have faulty ignition coils, replacing them should be a top priority.

The cost of replacement, as it is in most car parts, depends on the model and make of the vehicle. In the case of ignition coils, this cost may vary even more because different ignition coil types are used in different cars.

Coil-Near-Plug and Coil-On-Plug, are the most common ignition coil types. The Coil-On-Plug type is, however, more popular than the other in modern vehicles.

Purchasing a new ignition coil will cost between $20 and $40. However, they can be sold in sets in some offers, reducing the cost per coil.

Changing the properly operating ignition coils in your vehicle won’t be necessary if the others work fine. However, depending on the model of your car, accessing the ignition coil location could be quite difficult.

In this case, it may be best if you replace all ignition coils as a whole to avoid trying to locate them again if another develops a fault.

Replacing ignition coils in most vehicles doesn’t require too much labor, and the labor cost will range between $50 and $100.

Changing your ignition coils isn’t very difficult. If you’ve worked with cars in the past, you can most likely change them yourself, so you won’t have to spend money on labor costs.

If you intend to change it yourself, make sure you do so in a secure environment, and check your car’s official instructions for guidelines on replacing ignition coils. This is because these coils have a lot of voltage passing through them.

Also Read: How Much Does Evaporator Coil Replacement Cost?

Frequently Asked Questions – Ignition Coil Replacement

How much does it cost to replace the ignition coil?

Replacing only one ignition coil costs between $20 and $40. Although the labor cost depends on your car model, it will usually cost between 50 and 100 dollars.

Is it worth replacing the ignition coil?

You should replace your ignition coils if you notice a trace of arcing, cracks, or any other damage which could cause the coils to be short.

Can I change an ignition coil myself?

Your ‘Service Engine’ light may be illuminated, and your car may stall or even be unable to start. Although you can easily change a faulty ignition coil, remember that you are dealing with very high voltages; thus, you must disconnect the battery before starting.

How long does it take to change ignition coils?

It only takes about half an hour to remove your spark plug cables and your ignition coil (some bolts) and reverse the process to install your new cables and coil.

Can you replace ignition coils without replacing spark plugs?

Suppose you’re simply replacing the spark plugs because you’re carrying out regular maintenance service. In that case, the ignition coils don’t need to be replaced along with the plugs, except if you notice signs that the coils are developing faults.

Conclusion – Ignition Coil Replacement

The ignition coils have an important role in the ignition systems of gas-powered internal combustion engines.

The signs of a faulty spark plug overlap with most ignition coil problems. This includes difficulty starting your engine, misfires, and rough idle.

The ignition coils in some vehicle models are slightly more difficult to access. In these models, it’s most likely best to replace all your ignition coils simultaneously.

In most instances, only the faulty ignition coil will need to be replaced, but buying a complete set could get you a better deal.

Scott Greene is a seasoned automotive technician for over 5 years and has been deep into advanced automotive diagnostics for a couple of years. He Loves writing about Automotive Diagnostics and Repair, Trouble codes, Buyer guides for various car parts and accessories, and lots more. 

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