Subaru Outback 2012: Ignition Coil Replacement Guide

Nov 13, 2025 by Alex Braham 53 views

Hey guys! Today, we're diving into a common issue for Subaru Outback 2012 owners: ignition coil replacement. If your trusty Outback is starting to misfire or run rough, chances are your ignition coils might be the culprit. Don't worry, we'll walk you through everything you need to know, from diagnosing the problem to replacing the coils yourself. So, let's get started and keep your Subaru running smoothly!

Understanding the Ignition Coil

Let's kick things off by understanding what an ignition coil actually does. In simple terms, the ignition coil is a vital part of your car's ignition system. Its main job is to transform the relatively low voltage from your car's battery into the high voltage needed to create a spark at the spark plugs. This spark is what ignites the air-fuel mixture in the engine cylinders, which in turn powers your car. Without a properly functioning ignition coil, your engine won't be able to ignite the fuel, leading to misfires, rough idling, and a decrease in overall performance.

Inside the ignition coil, there are two main windings: the primary and secondary windings. When the car's computer (ECU) sends a signal, it interrupts the current flowing through the primary winding. This interruption causes a magnetic field to collapse, inducing a high-voltage current in the secondary winding. This high-voltage is then sent to the spark plug via the spark plug wire (or directly in some newer designs), creating the spark that ignites the fuel. Over time, ignition coils can degrade due to heat, vibration, and electrical stress, leading to failures.

The role of the ignition coil is critical to ensure your car runs efficiently and reliably. A faulty coil can lead to a variety of problems, including reduced fuel economy, increased emissions, and potential damage to other engine components. Regular maintenance and timely replacement of worn-out ignition coils are essential to keep your Subaru Outback 2012 performing at its best. Keep an eye out for symptoms like a flashing check engine light, which often indicates a misfire caused by a bad coil. Addressing these issues promptly can save you from more costly repairs down the road. Remember, a healthy ignition system means a happy and smooth-running Outback!

Symptoms of a Failing Ignition Coil

Recognizing the symptoms of a failing ignition coil is crucial for maintaining your Subaru Outback 2012's performance. Keep an eye (and ear) out for these telltale signs:

Engine Misfires: This is one of the most common symptoms. You might feel a sudden jerk or stumble in the engine's performance, especially during acceleration. Misfires occur when one or more cylinders fail to ignite the air-fuel mixture properly. This can be due to a weak or non-existent spark from a failing ignition coil.
Rough Idling: If your Outback is idling roughly, meaning the engine is shaking or vibrating more than usual when stopped, it could indicate a faulty ignition coil. The engine may struggle to maintain a consistent idle speed, leading to noticeable vibrations.
Decreased Fuel Economy: A failing ignition coil can cause the engine to burn fuel less efficiently. You might notice that you're filling up your gas tank more often than usual, even if your driving habits haven't changed. This is because the engine isn't burning fuel completely, wasting gas in the process.
Check Engine Light: The check engine light is your car's way of telling you something is wrong. If an ignition coil is failing, the check engine light will often illuminate. You can use an OBD-II scanner to read the diagnostic trouble codes (DTCs) and confirm if it's related to the ignition system. Common codes include P0300 (random misfire), P0301 (misfire in cylinder 1), and so on.
Loss of Power: A failing ignition coil can lead to a noticeable loss of power, especially when accelerating or climbing hills. The engine may feel sluggish and unresponsive, making it difficult to maintain speed. This is because the engine isn't producing its full potential power due to incomplete combustion.
Engine Hesitation: You might experience hesitation when you press the accelerator pedal. The engine may take a moment to respond, or it may feel like it's struggling to accelerate. This hesitation can be particularly noticeable when trying to merge onto a highway or pass another vehicle.

Addressing these symptoms promptly can prevent further damage to your engine and improve your car's overall performance. If you notice any of these signs, it's a good idea to have your ignition coils inspected by a qualified mechanic or to perform a DIY inspection if you're comfortable working on cars. Ignoring these symptoms can lead to more serious problems, such as damage to the catalytic converter or other engine components.

Tools and Parts Needed

Before you begin the ignition coil replacement, make sure you have all the necessary tools and parts. Here’s a comprehensive list to get you started:

New Ignition Coils: Purchase replacement ignition coils specifically designed for your 2012 Subaru Outback. It's generally recommended to replace all the coils at the same time to ensure consistent performance and avoid future issues. High-quality aftermarket coils or OEM (Original Equipment Manufacturer) coils are good choices.
Socket Set: A socket set with various sizes is essential for removing the bolts that secure the ignition coils. A 10mm socket is commonly used, but it's good to have a range of sizes on hand.
Ratchet: Use a ratchet to turn the sockets and loosen or tighten the bolts. A standard ratchet with a comfortable grip will make the job easier.
Extension Bars: Extension bars can help you reach bolts that are in tight or hard-to-reach places. Different lengths of extension bars can be useful.
Screwdrivers: You might need both flathead and Phillips head screwdrivers to remove any plastic covers or clips that are in the way.
OBD-II Scanner: An OBD-II scanner is helpful for reading and clearing diagnostic trouble codes (DTCs). After replacing the ignition coils, you can use the scanner to clear any misfire codes that may have been stored.
Multimeter: A multimeter can be used to test the old ignition coils to confirm if they are indeed faulty. This can help you diagnose the problem more accurately.
Work Gloves: Protect your hands from dirt, grease, and sharp edges by wearing work gloves.
Safety Glasses: Safety glasses are important to protect your eyes from debris while working on the engine.
Pen and Paper: Keep a pen and paper handy to label and keep track of the order of the ignition coils and any other parts you remove. This can be helpful when reassembling everything.
Torque Wrench: A torque wrench is important for tightening the bolts to the manufacturer's specified torque. This prevents over-tightening, which can damage the bolts or the engine.
Dielectric Grease: Apply dielectric grease to the spark plug boots to ensure a good electrical connection and prevent corrosion.

Having all these tools and parts on hand will make the ignition coil replacement process smoother and more efficient. Before starting the job, double-check that you have everything you need and that all the tools are in good working condition. This will save you time and frustration in the long run.

Step-by-Step Replacement Guide

Replacing the ignition coils on your 2012 Subaru Outback is a task you can tackle at home with the right tools and a bit of patience. Here’s a step-by-step guide to help you through the process:

Preparation: Start by ensuring the engine is cool. Disconnect the negative battery terminal to prevent any electrical accidents. Gather all the necessary tools and parts listed earlier and lay them out within easy reach.
Locate the Ignition Coils: The ignition coils are typically located on top of the engine, directly above the spark plugs. On the Subaru Outback 2012, they are usually easily accessible once you remove any plastic engine covers.
Remove Engine Covers: Use a screwdriver or socket to remove any plastic engine covers that are obstructing access to the ignition coils. Set the covers aside in a safe place.
Disconnect Electrical Connectors: Each ignition coil has an electrical connector attached to it. Gently press the release tab on the connector and pull it off the coil. Be careful not to pull on the wires themselves. Label each connector with a piece of tape indicating which cylinder it belongs to. This will help you reconnect them correctly later.
Remove the Ignition Coils: Use a socket and ratchet to remove the bolts that secure the ignition coils to the engine. Once the bolts are removed, gently pull the ignition coils straight up to remove them. If they are stuck, try twisting them slightly while pulling. Again, label each coil with the cylinder number to avoid confusion during reassembly.
Inspect the Spark Plugs: With the ignition coils removed, take the opportunity to inspect the spark plugs. If they appear worn or damaged, now is a good time to replace them. Use a spark plug socket to remove and install the spark plugs.
Install New Ignition Coils: Apply a small amount of dielectric grease to the inside of the spark plug boots on the new ignition coils. This will help ensure a good electrical connection and prevent corrosion. Install the new ignition coils in the reverse order of removal. Make sure they are fully seated and aligned properly.
Tighten the Bolts: Use a torque wrench to tighten the bolts to the manufacturer's specified torque. This is important to prevent over-tightening, which can damage the bolts or the engine. Refer to your Subaru Outback 2012 repair manual for the correct torque specifications.
Reconnect Electrical Connectors: Reconnect the electrical connectors to the ignition coils. Make sure they click into place and are securely attached.
Reinstall Engine Covers: Reinstall any plastic engine covers that you removed earlier. Tighten the bolts or screws securely.
Reconnect Battery: Reconnect the negative battery terminal.
Clear Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to clear any diagnostic trouble codes (DTCs) that may have been stored in the engine control unit (ECU).
Test Drive: Start the engine and let it idle for a few minutes. Listen for any unusual noises or vibrations. Take the car for a test drive to ensure that the engine is running smoothly and that there are no misfires.

By following these steps carefully, you can successfully replace the ignition coils on your 2012 Subaru Outback and restore its performance. If you encounter any difficulties or are unsure about any part of the process, it’s always best to consult a qualified mechanic.

Troubleshooting Tips

Even with a detailed guide, you might run into a few snags during the ignition coil replacement. Here are some troubleshooting tips to help you out:

Engine Still Misfiring: If your engine is still misfiring after replacing the ignition coils, double-check that you installed the coils correctly and that the electrical connectors are securely attached. Also, consider the possibility that the spark plugs may be faulty and need to be replaced. Use an OBD-II scanner to check for any new diagnostic trouble codes (DTCs) that may provide additional clues.
Difficulty Removing Ignition Coils: If you're having trouble removing the ignition coils, try twisting them gently while pulling upwards. You can also use a small amount of penetrating oil to help loosen any corrosion or buildup that may be preventing them from coming out. Be patient and avoid using excessive force, as this could damage the coils or the engine.
Electrical Connectors Won't Stay Connected: If the electrical connectors won't stay connected to the ignition coils, inspect the connectors for any damage or corrosion. Clean the connectors with electrical contact cleaner and make sure the release tab is functioning properly. If the connectors are damaged, you may need to replace them.
Check Engine Light Stays On: If the check engine light remains on after replacing the ignition coils and clearing the DTCs, use an OBD-II scanner to recheck for any new codes. The code could be related to another issue, such as a faulty oxygen sensor or a vacuum leak. Address any new codes as needed.
Rough Idling Persists: If your engine is still idling roughly after replacing the ignition coils, check for other potential causes, such as a dirty or faulty mass airflow (MAF) sensor, a vacuum leak, or a problem with the fuel injectors. Cleaning the MAF sensor or addressing any vacuum leaks may resolve the issue.
Loss of Power Continues: If you're still experiencing a loss of power after replacing the ignition coils, consider checking the fuel filter and fuel pump. A clogged fuel filter or a weak fuel pump can restrict fuel flow to the engine, leading to a loss of power. Replacing the fuel filter or fuel pump may improve performance.

By keeping these troubleshooting tips in mind, you can overcome common challenges and ensure a successful ignition coil replacement on your 2012 Subaru Outback. If you're still having trouble, don't hesitate to seek assistance from a qualified mechanic.

Preventative Maintenance

To keep your Subaru Outback 2012 running smoothly and avoid future ignition coil problems, consider these preventative maintenance tips:

Regular Spark Plug Replacement: Follow the manufacturer's recommended maintenance schedule for spark plug replacement. Worn or fouled spark plugs can put extra strain on the ignition coils, leading to premature failure. Replacing the spark plugs at the recommended intervals can help prolong the life of the ignition coils.
Inspect Ignition Coils Regularly: Periodically inspect the ignition coils for any signs of damage, such as cracks, corrosion, or oil leaks. If you notice any issues, replace the affected coil promptly to prevent further damage.
Keep the Engine Clean: Keep the engine bay clean and free of debris. Dirt, oil, and other contaminants can cause the ignition coils to overheat and fail. Regularly clean the engine bay with a mild degreaser to keep everything in good condition.
Avoid Short Trips: Whenever possible, avoid taking frequent short trips. Short trips don't allow the engine to reach its optimal operating temperature, which can lead to condensation and corrosion in the ignition system. Combine errands and take longer trips when possible.
Use Quality Fuel: Use high-quality fuel from reputable gas stations. Low-quality fuel can contain contaminants that can damage the ignition system and other engine components. Using premium fuel can help keep your engine running smoothly and efficiently.
Address Engine Problems Promptly: Address any engine problems, such as misfires or rough idling, promptly. Ignoring these issues can put extra strain on the ignition coils and lead to premature failure. Diagnose and repair any engine problems as soon as they arise.

By following these preventative maintenance tips, you can help ensure the long-term reliability of your Subaru Outback 2012's ignition system and avoid costly repairs down the road. Regular maintenance is key to keeping your car running smoothly and efficiently.