🔧 Crosstrek - Spark Plug Replacement

On your Crosstrek, the spark plugs sit on the sides of the engine under the ignition coils. Replacing them restores smooth starting, idle quality, and fuel economy, especially as mileage builds up.

Difficulty Level: Intermediate | Estimated Time: 1.5-3.0 hours

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⚠️ Safety & Precautions

• ⚠️ Work on a completely cool engine to avoid burns and stripped threads.
• ⚠️ Disconnect the negative battery cable to prevent accidental shorts.
• ⚠️ Do not over-tighten spark plugs; aluminum cylinder head threads strip easily.
• ⚠️ Keep dirt out of the spark plug holes; blow out debris before removing plugs.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• Floor jack (rated 2-ton minimum)
• Jack stands (rated 2-ton minimum)
• Wheel chocks
• 10mm socket
• 10mm wrench
• 12mm socket
• 3/8" drive ratchet
• 3/8" drive torque wrench (10-30 ft-lbs)
• 14mm thin-wall spark plug socket (3/8" drive)
• 3/8" drive extension set (3", 6", 10")
• 3/8" drive universal joint
• Flathead screwdriver
• Phillips screwdriver
• Picks/hook tool (specialty)
• Compressed air or hand air blower
• Flashlight

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs (correct fit for your Crosstrek) - Qty: 4
• Dielectric grease - Qty: 1

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📋 Before You Begin

• Park on level ground, shift to Park, and set the parking brake.
• Let the engine cool fully (ideally 1+ hour after driving).
• Use a 10mm wrench to disconnect the negative battery terminal and move it aside so it can’t spring back.
• Tip: Replace one plug at a time to avoid mix-ups.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover (if equipped)

• Pull straight up by hand to pop the cover off its grommets (no tools usually needed).
• Set it aside where it won’t get stepped on.

Step 2: Create room on the passenger side (right side)

• Use a flathead screwdriver or Phillips screwdriver to loosen the hose clamp(s) on the intake snorkel/duct.
• Use a 10mm socket to remove any 10mm bolts holding the duct or resonator (if present).
• Lift the ducting out of the way for better access to the right-side ignition coils.
• Tip: Take a quick photo before removing hoses.

Step 3: Replace the right-front spark plug (Cylinder 1)

• Find the ignition coil on the right-front side of the engine.
• Press the connector lock and unplug the coil connector. If it’s stubborn, use a picks/hook tool (specialty) gently to lift the lock tab (don’t break it).
• Use a 10mm socket to remove the ignition coil hold-down bolt.
• Twist the coil slightly and pull it straight out. (The coil boot is the rubber “tube” that seals over the plug.)
• Use compressed air or hand air blower to blow out dirt around the plug hole.
• Use a 14mm thin-wall spark plug socket, 3/8" drive ratchet, and a 6" extension to loosen and remove the spark plug.
• Install the new plug by lowering it into the hole with the spark plug socket and extension, then thread it in by hand (no ratchet yet) to avoid cross-threading.
• Use a 3/8" drive torque wrench to tighten the spark plug: Torque to 21 N·m (15 ft-lbs).
• Put a small smear of dielectric grease inside the coil boot (helps prevent moisture and makes future removal easier).
• Reinstall the coil and hold-down bolt using a 10mm socket: Torque to 7.5 N·m (5.5 ft-lbs).
• Reconnect the coil electrical connector until it clicks.

Step 4: Replace the right-rear spark plug (Cylinder 3)

• Repeat the same process as Step 3 on the right-rear coil.
• Use a 3/8" drive universal joint and a 10" extension if the angle is tight.
• Tighten the spark plug: Torque to 21 N·m (15 ft-lbs).
• Tighten the coil bolt: Torque to 7.5 N·m (5.5 ft-lbs).

Step 5: Create room on the driver side (left side)

• Use a 10mm socket to remove the battery hold-down clamp (if equipped).
• Use a 10mm socket to remove the battery terminals (negative first was already disconnected; remove positive next if needed), then lift the battery out carefully.
• Use a 10mm socket to remove the battery tray (if it blocks access).
• Tip: Batteries are heavy—lift with your legs.

Step 6: Replace the left-front spark plug (Cylinder 2)

• Unplug the left-front ignition coil connector.
• Use a 10mm socket to remove the coil hold-down bolt.
• Pull the coil out, then blow out the plug well using compressed air or hand air blower.
• Use a 14mm thin-wall spark plug socket, 3/8" drive ratchet, and extensions to remove the old plug.
• Hand-thread the new plug first, then torque it: Torque to 21 N·m (15 ft-lbs).
• Apply a small amount of dielectric grease inside the coil boot.
• Reinstall coil and torque the bolt: Torque to 7.5 N·m (5.5 ft-lbs).
• Reconnect the coil connector until it clicks.

Step 7: Replace the left-rear spark plug (Cylinder 4)

• Repeat the same process on the left-rear coil.
• Use a 3/8" drive universal joint and longer extension if needed.
• Tighten the spark plug: Torque to 21 N·m (15 ft-lbs).
• Tighten the coil bolt: Torque to 7.5 N·m (5.5 ft-lbs).

Step 8: Reassemble the intake parts and battery

• Reinstall the battery tray using a 10mm socket (if removed).
• Reinstall the battery and hold-down using a 10mm socket.
• Reconnect battery terminals using a 10mm socket (positive first, negative last).
• Reinstall the intake ducting and tighten clamps using a flathead screwdriver or Phillips screwdriver.
• Reinstall the engine cover by pressing it down onto the grommets.

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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 air leaks near the intake ducting (hissing). If you hear one, re-tighten the clamps with a flathead screwdriver.
• If the check engine light comes on or it runs rough, shut it off and re-check that every coil connector is fully clicked in.
• Tip: A missed coil connector mimics a “bad plug.”

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💰 DIY vs Shop Cost

Shop Cost: $300-$550 (parts + labor)

DIY Cost: $50-$120 (parts only)

You Save: $250-$430 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.5-3.0 hours.

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🎯 Ready to get started?

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