🔧 Outback - Spark Plug Replacement

Replacing the spark plugs on your Outback helps restore smooth idle, strong acceleration, and proper fuel economy. The 3.6L flat-six uses six spark plugs, and access is tight because the engine sits wide in the engine bay.

Difficulty Level: Intermediate | Estimated Time: 2.5-4 hours

---

⚠️ Safety & Precautions

• ⚠️ Work only on a fully cool engine; the cylinder heads and exhaust parts can burn you.
• ⚠️ Disconnect the negative battery cable before unplugging ignition coils.
• ⚠️ Keep dirt out of the spark plug wells; debris can fall into the engine when a plug is removed.
• ⚠️ Do not force spark plugs. Cross-threading means the plug is going in crooked and can damage the cylinder head.
• ⚠️ Use only the correct iridium spark plugs for your Outback; do not install copper plugs.

---

🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 12mm socket
• 3/8-inch drive ratchet
• 3/8-inch drive torque wrench
• 5/8-inch spark plug socket with rubber insert
• 3-inch 3/8-inch drive extension
• 6-inch 3/8-inch drive extension
• 3/8-inch drive universal joint
• Flat-blade screwdriver
• Needle-nose pliers
• Compressed air blow gun
• Spark plug gap gauge
• Magnetic pickup tool
• Dielectric grease
• Anti-seize compound
• Mechanic gloves
• Safety glasses
• Fender cover

---

🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs - Qty: 6
• Intake duct clamp clips - Qty: As needed

---

📋 Before You Begin

• 🅿️ Park your Outback on level ground, set the parking brake, and let the engine cool completely.
• 🔋 Open the hood and disconnect the negative battery cable using a 10mm socket.
• 🧤 Put on safety glasses and gloves before working around the battery, intake ducting, and ignition coils.
• 📏 Check the new plugs with a spark plug gap gauge. A gap gauge measures the small air gap at the plug tip. Use the plug manufacturer’s preset spec if the plug is marked “do not gap.”
• 🧼 Blow loose dirt away from the top and sides of the engine using a compressed air blow gun.

---

🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the Engine Cover

• Use both hands to lift the plastic engine cover straight upward from its rubber mounting grommets.
• Set the cover aside where it will not get stepped on.
• Tip: Lift evenly to avoid cracking it.

Step 2: Disconnect the Negative Battery Cable

• Use a 10mm socket to loosen the nut on the negative battery terminal.
• Move the cable away from the battery post so it cannot accidentally touch.
• This prevents accidental coil activation while your hands are near the ignition system.

Step 3: Remove the Air Intake Ducting for Access

• Use a flat-blade screwdriver to loosen the intake hose clamp at the throttle body.
• Use a flat-blade screwdriver to loosen the clamp at the air filter box side.
• Disconnect any small hose or clip attached to the intake duct using needle-nose pliers if needed.
• Lift the intake duct out of the way and place it aside.
• Tip: Take a phone photo before removing hoses.

Step 4: Identify the Ignition Coils

• The 3.6L flat-six has three ignition coils on each side of the engine.
• An ignition coil is the small electrical part mounted directly over each spark plug.
• Use a fender cover to protect the paint while you lean over the fender.

Step 5: Remove the Passenger-Side Ignition Coils

• Press the electrical connector tab on the first coil and unplug it by hand.
• If the connector is tight, gently help the tab with a flat-blade screwdriver.
• Use a 10mm socket and 3/8-inch drive ratchet to remove the coil retaining bolt.
• Twist the coil gently by hand, then pull it straight out.
• Repeat for the remaining passenger-side coils.

Step 6: Clean the Spark Plug Wells

• Use a compressed air blow gun to blow dirt out of each spark plug well before removing the plugs.
• A spark plug well is the deep tube where the plug sits inside the cylinder head.
• Wear safety glasses because dust may blow back toward your face.

Step 7: Remove the Passenger-Side Spark Plugs

• Use a 5/8-inch spark plug socket with rubber insert, 3-inch 3/8-inch drive extension, and 3/8-inch drive ratchet.
• For tighter angles, add the 3/8-inch drive universal joint. A universal joint lets the socket bend slightly to reach the plug.
• Turn the plug counterclockwise slowly until it is free.
• Lift the plug out using the spark plug socket or a magnetic pickup tool.
• Remove one plug at a time so you do not mix up your work area.

Step 8: Install the Passenger-Side Spark Plugs

• Apply a tiny amount of anti-seize compound to the new plug threads only if the plug manufacturer allows it. Many modern iridium plugs already have coated threads.
• Place the new spark plug into the 5/8-inch spark plug socket with rubber insert.
• Start the plug by hand using the 3-inch 3/8-inch drive extension only. Do not use the ratchet at first.
• Turn it clockwise several full turns by hand to make sure it threads smoothly.
• Use a 3/8-inch drive torque wrench to tighten each plug to Torque to 21 Nm (15 ft-lbs).
• Tip: If it feels rough, stop immediately.

Step 9: Reinstall the Passenger-Side Ignition Coils

• Apply a small dab of dielectric grease inside the rubber boot of each ignition coil.
• Push each coil straight down over its spark plug until seated.
• Use a 10mm socket and 3/8-inch drive torque wrench to tighten each coil bolt to Torque to 8 Nm (71 in-lbs).
• Reconnect each coil electrical connector until it clicks.

Step 10: Create Access on the Driver Side

• Use a 10mm socket to remove any small brackets or harness retainers blocking direct hand access to the driver-side coils.
• Move wiring gently aside by hand; do not pull hard on the harness.
• If a plastic clip resists, use needle-nose pliers to release it carefully.
• Tip: Label bolts if several are removed.

Step 11: Remove the Driver-Side Ignition Coils

• Press each coil connector tab by hand and unplug it.
• Use a 10mm socket and 3/8-inch drive ratchet to remove each coil retaining bolt.
• Twist each coil gently, then pull it out of the spark plug well.
• The rear driver-side coil is the tightest; use patience and small hand movements.

Step 12: Remove the Driver-Side Spark Plugs

• Use a compressed air blow gun to clean the plug wells before removal.
• Use a 5/8-inch spark plug socket with rubber insert, 3-inch 3/8-inch drive extension, 3/8-inch drive universal joint, and 3/8-inch drive ratchet.
• Turn each plug counterclockwise slowly until loose.
• Lift each plug out with the socket or a magnetic pickup tool.
• Inspect the old plugs for oil, heavy carbon, or cracked porcelain.

Step 13: Install the Driver-Side Spark Plugs

• Place each new plug in the 5/8-inch spark plug socket with rubber insert.
• Start each plug by hand using the 3-inch 3/8-inch drive extension to avoid cross-threading.
• Once seated by hand, use a 3/8-inch drive torque wrench to tighten each plug to Torque to 21 Nm (15 ft-lbs).
• Do not over-tighten. The cylinder head is aluminum and can be damaged.

Step 14: Reinstall the Driver-Side Ignition Coils

• Apply a small dab of dielectric grease inside each ignition coil boot.
• Push each coil straight onto its spark plug by hand.
• Use a 10mm socket and 3/8-inch drive torque wrench to tighten each coil bolt to Torque to 8 Nm (71 in-lbs).
• Plug in each electrical connector until it clicks.

Step 15: Reinstall Brackets and Intake Ducting

• Use a 10mm socket to reinstall any brackets or harness retainers removed for access.
• Use a flat-blade screwdriver to reinstall and tighten the intake duct clamps.
• Reconnect any small hoses or clips using needle-nose pliers if needed.
• Make sure the intake duct is fully seated at both ends to prevent unmetered air leaks.

Step 16: Reconnect the Battery and Reinstall the Engine Cover

• Place the negative battery cable back onto the battery post.
• Use a 10mm socket to tighten the battery terminal snugly.
• Push the engine cover down by hand until it seats into the rubber grommets.

---

✅ After Repair

• ✅ Start your Outback and let it idle for 1-2 minutes.
• 👂 Listen for misfires, clicking, hissing, or rough idle.
• 🔍 Check that every ignition coil connector is fully clicked in.
• 🔍 Check the intake duct clamps and hoses for a secure fit.
• 🚗 Take a gentle 10-minute test drive, then recheck for warning lights.
• ⚠️ If the check engine light flashes, stop driving and recheck coil connectors and plug installation.

---

💰 DIY vs Shop Cost

Shop Cost: $450-$750 (parts + labor)

DIY Cost: $80-$180 (parts only)

You Save: $370-$570 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2-3 hours.

---

🎯 Ready to get started?

HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.