🔧 Forester - Ignition Coil Replacement

Your Forester’s ignition coils sit on top of the spark plugs and create the high voltage needed to fire the engine. Replacing a weak or failed coil can fix misfires, rough idle, and flashing check engine light.

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

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⚠️ Safety & Precautions

• ⚠️ Let the engine cool fully before working near the turbo/intercooler.
• ⚠️ Disconnect the negative battery terminal to prevent accidental shorting.
• ⚠️ Don’t pull on wiring; release connectors by the lock tab.
• ⚠️ If the check engine light is flashing, avoid driving until fixed (can damage the catalytic converter).

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 12mm socket
• 3/8" ratchet
• 3/8" torque wrench (5–30 ft-lbs range)
• 6" socket extension (3/8")
• Flathead screwdriver
• 8mm nut driver
• Needle-nose pliers
• Trim clip tool
• Work light
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 4
• Dielectric grease packet - Qty: 1

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📋 Before You Begin

• Park on level ground, shift to Park, and set the parking brake.
• Open the hood and let the engine cool until you can touch nearby metal parts comfortably.
• Disconnect the battery: use a 10mm socket to remove the negative terminal and tuck it aside.
• If you’re replacing only one coil, note which cylinder had the misfire code before starting.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the top-mount intercooler (for access)

• Use an 8mm nut driver or flathead screwdriver to loosen the hose clamps at the throttle-body coupler and turbo outlet coupler.
• Use a 12mm socket to remove the bypass valve bolts on the intercooler.
• Use needle-nose pliers to release any small hose clamps (if equipped), then slide hoses off gently.
• Lift the intercooler up and out carefully. Wiggle gently—don’t force it.

Step 2: Unplug one ignition coil

• Locate a coil on the side of the engine (one coil per cylinder).
• Press the connector lock tab and pull the connector straight off the coil.
• If it’s stuck, use a trim clip tool to gently help the tab release (do not pry hard on the wires).

Step 3: Remove the ignition coil retaining bolt

• Use a 10mm socket, 3/8" ratchet, and 6" extension to remove the coil hold-down bolt.
• Set the bolt aside where it won’t fall into the engine bay.

Step 4: Remove the ignition coil

• Twist the coil slightly left/right to break the seal, then pull it straight off the spark plug.
• Check the coil boot for oil or water. If you see oil inside the boot, stop and plan for diagnosis (can indicate a valve cover leak).

Step 5: Install the new ignition coil

• Apply a tiny smear of dielectric grease inside the new coil boot. Dielectric grease is a non-conductive grease that helps prevent moisture and makes future removal easier.
• Push the coil straight onto the spark plug until fully seated.
• Reinstall the hold-down bolt using a 10mm socket and 3/8" torque wrench: Torque to 7.5 Nm (5.5 ft-lbs).

Step 6: Reconnect the coil electrical connector

• Push the connector on until you feel/hear a click.
• Give it a gentle tug to confirm it’s locked.

Step 7: Repeat for the remaining coils

• Replace coils one at a time so you don’t mix up connectors.
• Use the same process: unplug, remove 10mm bolt, swap coil, torque to 7.5 Nm (5.5 ft-lbs), reconnect.

Step 8: Reinstall the intercooler

• Set the intercooler back into place, making sure both couplers line up correctly.
• Reinstall bypass valve bolts using a 12mm socket and snug them evenly.
• Tighten the hose clamps using an 8mm nut driver or flathead screwdriver.
• Double-check that all hoses are fully seated and clamps are tight to prevent boost leaks.

Step 9: Reconnect the battery

• Reconnect the negative battery terminal using a 10mm socket and tighten snugly.

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✅ After Repair

• Start the engine and let it idle for 1–2 minutes. It should run smooth with no shaking.
• Listen for hissing near the intercooler hoses (can indicate a boost/air leak).
• If you have a scan tool, clear misfire codes and confirm none return after a short drive.
• If the check engine light still flashes or it still misfires, stop driving and recheck coil connectors and intercooler hose clamps.

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💰 DIY vs Shop Cost

Shop Cost: $450-$900 (parts + labor)

DIY Cost: $220-$520 (parts only)

You Save: $230-$380 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?

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