🔧 Impreza - Ignition Coil Replacement

Your Impreza uses one ignition coil per cylinder. Replacing a weak or failed coil can fix misfires, rough idle, flashing check engine light, and loss of power.

Difficulty Level: Intermediate | Estimated Time: 0.8-1.5 hours

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⚠️ Safety & Precautions

• ⚠️ Let the engine cool fully; coils sit near hot metal parts.
• ⚠️ Disconnect the battery negative terminal to prevent accidental shorts.
• ⚠️ If the check engine light is flashing, avoid driving until repaired (active misfire can damage the catalytic converter).
• ⚠️ Pull on the connector body, not the wires, to avoid breaking the harness.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 10mm wrench
• 12mm socket
• 3/8" drive ratchet
• 3" extension
• Torque wrench (5-25 Nm range)
• Flathead screwdriver
• Needle-nose pliers
• OBD2 scan tool
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

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

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📋 Before You Begin

• Park on level ground, set the parking brake, and open the hood.
• Disconnect the battery: use a 10mm wrench to remove the negative terminal and move it aside so it can’t spring back.
• Replace coils one-at-a-time to avoid mix-ups.
• Assumption: Torque specs below match the common FB20 coil fastener spec used on this Impreza.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the air intake ducting (for access)

• Use a flathead screwdriver to loosen the intake hose clamp(s) and release any plastic clips.
• Use needle-nose pliers to slide spring clamps back on any small breather hose(s), then pull the hose(s) off gently.
• Lift the intake snorkel/duct out of the way so you can reach the coils more easily.

Step 2: Create room on the tight side (battery area)

• If access is tight, remove the battery hold-down: use a 10mm socket to remove the hold-down nuts and bracket.
• Use a 10mm wrench to remove the positive terminal, then lift the battery out carefully.
• If needed, remove the battery tray bolts with a 12mm socket and 3/8" ratchet.

Step 3: Unplug the ignition coil electrical connector

• Find the coil (one per cylinder) on the side/top area of each cylinder head.
• Press the connector lock tab and pull the connector straight off.
• Wiggle the connector—don’t yank wires.

Step 4: Remove the ignition coil

• Use a 10mm socket, 3" extension, and 3/8" ratchet to remove the coil mounting bolt.
• Twist the coil slightly, then pull it straight out. (The rubber boot grips the spark plug tightly.)

Step 5: Install the new ignition coil

• Put a very small 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 it fully seats.
• Install the mounting bolt by hand first to avoid cross-threading, then tighten with a 10mm socket.
• Torque to 6.4 Nm (4.7 ft-lbs) using a torque wrench.

Step 6: Reconnect the coil connector

• Push the electrical connector on until it clicks and locks.

Step 7: Repeat for remaining coils (if replacing more than one)

• Repeat Steps 3-6 for any other coil(s) you’re replacing.

Step 8: Reinstall battery and intake parts

• Reinstall the battery tray (if removed) using a 12mm socket.
• Reinstall the battery and hold-down using a 10mm socket.
• Reconnect terminals with a 10mm wrench (positive first, negative last).
• Reinstall the intake ducting and tighten clamps with a flathead screwdriver.

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✅ After Repair

• Start the engine and let it idle for 1-2 minutes. It should run smooth with no shaking.
• Use an OBD2 scan tool to clear misfire codes if needed, then confirm they don’t return.
• Take a short test drive and recheck that all intake clamps/hoses are snug (no hissing/whistling).

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💰 DIY vs Shop Cost

Shop Cost: $350-$700 (parts + labor)

DIY Cost: $60-$320 (parts only, depending on 1 vs 4 coils)

You Save: $150-$400 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.8-1.5 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.