🔧 Impreza - Ignition Coil Replacement

Your Impreza uses one ignition coil per cylinder (coil-on-plug). Replacing a bad coil restores smooth running, fixes misfires, and can turn off a flashing/steady 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 starting; coils sit near hot parts.
• ⚠️ Disconnect the negative battery terminal to avoid accidental shorts.
• ⚠️ Pull on the connector body, not the wires, to prevent harness damage.
• ⚠️ Keep dirt out of the spark plug tubes; blow debris away before removing a coil.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 1/4" drive ratchet
• 3" socket extension
• Universal joint swivel adapter
• Torque wrench (2–25 Nm range)
• Flat-blade screwdriver
• Trim clip remover
• Needle-nose pliers
• Shop rags
• Compressed air blow gun
• Safety glasses
• Nitrile gloves

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 4 Replace as needed; pairs recommended
• Dielectric grease - 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 completely.
• Use a 10mm socket to disconnect the negative battery terminal and move it aside.
• Assumption: Stock intake system and no engine modifications.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover (if equipped)

• Lift the cover straight up by hand to release the rubber grommets, then set it aside.

Step 2: Create room to access the coils

• On the air box/intake duct area, loosen hose clamps using a flat-blade screwdriver and remove any clips with a trim clip remover.
• Move the intake snorkel/ducting out of the way as needed to reach the coil(s) you’re replacing.
• If one side feels too tight, remove the air box top using a 10mm socket and 1/4" drive ratchet.
• Tip: Take a quick photo before moving hoses.

Step 3: Unplug the ignition coil connector

• Locate the coil on the side of the engine (one per cylinder).
• Press the locking tab and pull the connector straight off by hand.
• If the tab is stubborn, gently help it with needle-nose pliers (do not crush the connector).
• Universal joint: A swivel that helps the socket angle in tight spaces.

Step 4: Remove the coil retaining bolt

• Use a 10mm socket, 3" socket extension, universal joint swivel adapter, and 1/4" drive ratchet to remove the coil bolt.
• Set the bolt somewhere safe (a magnetic tray is helpful if you have one).

Step 5: Remove the ignition coil

• Before pulling the coil, use compressed air blow gun to blow dirt away from the coil area.
• Grip the coil body and twist slightly, then pull it straight out.
• If it feels stuck, wiggle gently—don’t pry hard on plastic.

Step 6: Install the new ignition coil

• Put a very small smear of dielectric grease inside the new coil boot (the rubber cup that seals to the spark plug). This helps prevent sticking and moisture intrusion.
• Push the new coil straight into the spark plug tube until fully seated.
• Install the retaining bolt by hand first to avoid cross-threading.
• Use a torque wrench (2–25 Nm range) with a 10mm socket to tighten: Torque to 6.4 Nm (4.7 ft-lbs).

Step 7: Reconnect the electrical connector

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

Step 8: Repeat for any other coils being replaced

• Repeat Steps 3–7 for the remaining cylinder(s) as needed.
• Tip: Do one coil at a time to avoid mix-ups.

Step 9: Reinstall intake parts and reconnect the battery

• Reinstall the intake duct/air box parts using the 10mm socket, 1/4" drive ratchet, and flat-blade screwdriver for clamps.
• Reconnect the negative battery terminal using a 10mm socket.

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✅ After Repair

• Start the engine and let it idle for 1–2 minutes; it should run smooth.
• Check that the Check Engine Light is off (or no longer flashing).
• Take a short test drive and confirm there’s no hesitation under light acceleration.
• If the light stays on, you may need to clear stored codes with a scan tool and confirm the misfire is gone.

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💰 DIY vs Shop Cost

Shop Cost: $250-$650 (parts + labor)

DIY Cost: $80-$400 (parts only, depending on how many coils)

You Save: $170-$250+ by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.0-1.5 hours.

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🎯 Ready to get started?

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