🔧 Forester - Ignition Coil Replacement

The ignition coils sit on top of each spark plug and create the high-voltage spark your engine needs to run smoothly. Replacing a weak or failed coil can fix misfires, rough idle, and flashing check-engine lights.

Difficulty Level: Intermediate | Estimated Time: 1.0-2.0 hours

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⚠️ Safety & Precautions

• Let the engine cool fully before starting; coils sit near hot engine parts.
• Disconnect the negative battery terminal to prevent accidental shorts while unplugging connectors.
• Never pull on wiring; unplug connectors by the plastic connector body only.
• If the check-engine light is flashing, avoid driving until the misfire is fixed (can damage the catalytic converter).

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 1/4" drive ratchet
• 3" socket extension
• Torque wrench (2–20 Nm range)
• Flathead screwdriver
• Needle-nose pliers
• Trim clip removal tool
• Shop light
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 1 (or Qty: 4 if replacing all)
• Dielectric grease (silicone) - Qty: 1

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📋 Before You Begin

• Park on level ground and open the hood.
• Let the engine cool down completely.
• Use a 10mm socket to disconnect the negative battery terminal and set it aside so it can’t spring back.
• Take a quick photo of each connector first.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the top engine cover (if equipped)

• Remove the fasteners using a 10mm socket or release clips with a trim clip removal tool (cover style varies).
• Lift the cover straight up and set it aside.

Step 2: Create working room (air duct/battery as needed)

• Loosen intake duct clamps using a flathead screwdriver and move the duct/snorkel out of the way.
• If access is tight on the driver-side coils, remove the battery hold-down using a 10mm socket, then lift the battery out carefully.
• If small hose clips are in the way, squeeze and slide them back using needle-nose pliers.

Step 3: Unplug the ignition coil electrical connector

• Locate the coil on top of the valve cover (one per cylinder).
• Press the connector lock tab and pull the connector straight off by hand.
• If it’s stuck, gently help it with a flathead screwdriver on the connector body (do not pry on wires).

Step 4: Remove the coil retaining bolt

• Remove the single coil bolt using a 10mm socket, 1/4" drive ratchet, and 3" socket extension.
• Set the bolt somewhere safe so it doesn’t fall into the engine bay.

Step 5: Remove the ignition coil

• Twist the coil slightly to break the seal, then pull it straight out by hand.
• If it’s stubborn, keep twisting while pulling; avoid using tools on the coil boot.

Step 6: Install the new coil

• Put a tiny smear of dielectric grease (silicone) inside the rubber boot (this helps prevent sticking and moisture). Dielectric grease is a non-conductive silicone grease for electrical boots.
• Push the new coil straight onto the spark plug until it seats fully.
• Install the coil bolt by hand first (prevents cross-threading).
• Tighten the coil bolt using a torque wrench (2–20 Nm range): Torque to 6.4 Nm (4.7 ft-lbs).

Step 7: Reconnect the coil connector

• Push the connector on until you feel/hear it click into place.
• Gently tug the connector to confirm it’s locked.

Step 8: Repeat for the remaining coils

• Repeat Steps 3–7 for each coil you’re replacing.
• If one failed, consider replacing in pairs.

Step 9: Reinstall removed items

• Reinstall the battery (if removed) using a 10mm socket for the hold-down.
• Reconnect the negative battery terminal using a 10mm socket and tighten snugly.
• Reinstall the air duct/snorkel and tighten clamps using a flathead screwdriver.
• Reinstall the engine cover using a 10mm socket or trim clip removal tool.

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✅ After Repair

• Start the engine and let it idle for 1–2 minutes; it should run smooth with no shaking.
• Verify there is no fuel smell or loose intake duct (a loose duct can cause a rough idle).
• If the check-engine light stays on, scan for codes; a stored misfire code may need clearing after the repair.
• If misfire returns, the next common checks are spark plugs and coil connectors.

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💰 DIY vs Shop Cost

Shop Cost: $300-$750 (parts + labor)

DIY Cost: $80-$480 (parts only, depending on 1 vs 4 coils)

You Save: $220-$270 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.0-2.0 hours.

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🎯 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.