🔧 BRZ - Spark Plug Replacement

On your BRZ, the spark plugs sit deep in the cylinder heads and space is tight, so you’ll remove a few intake/battery parts and slightly lift the engine for access. Replacing worn plugs helps prevent misfires, rough idle, and poor fuel economy.

Difficulty Level: Advanced | Estimated Time: 3-5 hours

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⚠️ Safety & Precautions

• ⚠️ Work on a fully cool engine to avoid burns and damaged threads.
• ⚠️ Disconnect the negative battery terminal before unplugging ignition coils.
• ⚠️ Support the engine safely before loosening engine mount nuts.
• ⚠️ Never put any part of your body under a car supported only by a jack.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• Floor jack (rated 3-ton minimum)
• Jack stands (rated 3-ton minimum)
• Wheel chocks
• 10mm socket
• 12mm socket
• 14mm socket
• 3/8" ratchet
• 3/8" torque wrench
• 3/8" extension set (3", 6", 10")
• 3/8" swivel/universal joint
• 14mm thin-wall spark plug socket (magnetic or rubber insert)
• Flat trim tool
• Phillips screwdriver
• Needle-nose pliers
• Flashlight
• Feeler gauge set (wire-type)

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs (OEM-type) - Qty: 4
• Dielectric grease (small packet) - Qty: 1

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📋 Before You Begin

• Park on level ground, set the parking brake, and chock the rear wheels.
• Let the engine cool completely (at least 1-2 hours after driving).
• Use a 10mm socket to disconnect the negative battery cable and tuck it aside.
• Take photos before unplugging anything.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the intake tubing and airbox (right side access)

• Use a 10mm socket and Phillips screwdriver to loosen the intake hose clamp(s) and remove the intake snorkel/ducting.
• Unclip the airbox lid and remove the air filter using your hands.
• Use a 10mm socket to remove the airbox bolts, then lift the airbox out.

Step 2: Remove the battery (left side access)

• Use a 10mm socket to remove the battery hold-down bracket.
• Lift the battery out carefully (it’s heavier than it looks).
• Use a 10mm socket to remove the battery tray if it blocks access.

Step 3: Raise and support the front of the car

• Use a floor jack (rated 3-ton minimum) to lift the front at the proper jacking point.
• Set the car securely on jack stands (rated 3-ton minimum).
• Give the car a firm shake to confirm it’s stable.

Step 4: Support the engine from underneath

• Place the floor jack (rated 3-ton minimum) under the engine oil pan area with a sturdy flat pad.
• Raise the jack just until it gently supports the engine (do not lift yet).
• A swivel/universal joint is a pivoting adapter that helps sockets turn at an angle in tight spaces.

Step 5: Loosen engine mount nuts (to allow a small engine lift)

• Locate the left and right engine mount nuts from underneath.
• Use a 14mm socket and 3/8" ratchet to loosen (do not remove) the mount nuts several turns.
• Slowly lift the engine slightly using the floor jack (rated 3-ton minimum) until you gain access to the ignition coils.
• Lift only what you need for clearance.

Step 6: Remove ignition coil connectors and coil bolts (one cylinder at a time)

• On one side, use a flat trim tool to gently release the electrical connector lock tab, then unplug the coil.
• Use a 10mm socket to remove the ignition coil retaining bolt.
• Twist the coil boot slightly and pull the coil straight out.
• Do one plug at a time to avoid mix-ups.

Step 7: Remove the old spark plug

• Blow out or wipe away debris around the spark plug hole using a flashlight to inspect first.
• Install a 14mm thin-wall spark plug socket (magnetic or rubber insert) with a 3/8" extension set (3", 6", 10") and 3/8" swivel/universal joint.
• Use a 3/8" ratchet to loosen and remove the spark plug.

Step 8: Check gap and install the new spark plug

• Use a feeler gauge set (wire-type) to verify the new plug gap matches the plug maker’s spec for the BRZ.
• Thread the new plug in by hand first using the spark plug socket and an extension (no ratchet) so it doesn’t cross-thread.
• Tighten using a 3/8" torque wrench: Torque to 20 Nm (15 ft-lbs).
• Do not use anti-seize on plated plugs.

Step 9: Reinstall the ignition coil

• Apply a very small amount of dielectric grease inside the coil boot lip (not on the plug threads).
• Push the coil straight onto the plug until fully seated.
• Install the coil bolt using a 10mm socket, then finish with a 3/8" torque wrench: Torque to 10 Nm (7 ft-lbs).
• Reconnect the coil electrical connector until it clicks.

Step 10: Repeat for the remaining cylinders

• Repeat Steps 6-9 for the other plugs, lifting the engine a little more or less as needed with the floor jack.
• Swap sides as necessary (airbox side and battery side).

Step 11: Lower the engine and tighten engine mount nuts

• Slowly lower the engine using the floor jack until it fully sits on the mounts.
• Use a 14mm socket and 3/8" torque wrench to tighten the mount nuts: Torque to 55 Nm (41 ft-lbs).

Step 12: Reinstall battery and intake

• Reinstall the battery tray (if removed) using a 10mm socket.
• Reinstall the battery and hold-down using a 10mm socket.
• Reconnect terminals using a 10mm socket (negative cable last).
• Reinstall the airbox and intake tubing using a 10mm socket and Phillips screwdriver, and ensure clamps are tight.

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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 (hissing) near the intake tube/airbox.
• Test drive 10 minutes, then recheck that the intake clamps and battery hold-down are tight.
• If you get a check engine light or misfire, recheck coil connectors and coil seating.

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💰 DIY vs Shop Cost

Shop Cost: $350-$650 (parts + labor)

DIY Cost: $60-$140 (parts only)

You Save: $290-$510 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2.5-4.0 hours.

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🎯 Ready to get started?

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