🔧 Civic - Spark Plug Replacement

Replacing the spark plugs restores proper ignition, helps prevent misfires, and keeps your Civic running smoothly. On your Civic, the plugs sit under the ignition coils on top of the engine, so this is a straightforward top-side repair.

Difficulty Level: Beginner | Estimated Time: 1-2 hours

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⚠️ Safety & Precautions

• ⚠️ Let the engine cool completely before starting; spark plugs thread into the aluminum cylinder head and hot threads can be damaged.
• ⚠️ Disconnect the negative battery cable to reduce the chance of an electrical short while unplugging ignition coils.
• ⚠️ Do not drop anything into the spark plug wells; debris can fall into the engine when the plug is removed.
• ⚠️ Start all new spark plugs by hand only. Cross-threading means the plug goes in crooked and can damage the cylinder head.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 3/8-inch ratchet
• 3/8-inch torque wrench
• 6-inch 3/8-inch extension
• 14mm thin-wall spark plug socket
• Needle-nose pliers
• Compressed air nozzle
• Spark plug gap gauge
• Plastic trim tool
• Battery terminal wrench 10mm
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs - Qty: 4
• Dielectric grease - Qty: 1 small tube

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📋 Before You Begin

• Park your Civic on level ground and set the parking brake.
• Make sure the ignition is OFF and the key/fob is away from the vehicle.
• Open the hood and let the engine cool until it is safe to touch.
• Use a battery terminal wrench 10mm to disconnect the negative battery cable.
• A spark plug socket is a deep socket with a rubber insert or magnet that holds the plug so it does not fall.
• A torque wrench tightens a bolt or spark plug to a precise amount so it is not too loose or too tight.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the Engine Cover

• Use your hands or a plastic trim tool to lift the engine cover upward from its rubber mounting grommets.
• Set the cover aside where it will not get scratched or stepped on.
• Pull straight up, not sideways.

Step 2: Disconnect the Ignition Coil Connectors

• Locate the four ignition coils on top of the engine. An ignition coil sends high voltage to each spark plug.
• Use your fingers to press each connector release tab, then slide the connector off the coil.
• If a connector is stubborn, use needle-nose pliers gently on the release tab only.
• Do not pull on the wires themselves.

Step 3: Remove the Ignition Coils

• Use a 10mm socket, 3/8-inch ratchet, and 6-inch extension to remove the ignition coil hold-down bolts.
• Pull each ignition coil straight upward with a gentle twisting motion.
• Place the coils in order from left to right so they go back into the same cylinders.
• On installation, tighten the ignition coil bolts to Torque to 12 Nm (9 ft-lbs).

Step 4: Clean the Spark Plug Wells

• Put on safety glasses.
• Use a compressed air nozzle to blow dirt and grit out of each spark plug well.
• Keep your face away from the plug wells while blowing air.
• Clean wells protect the engine.

Step 5: Remove the Old Spark Plugs

• Use a 14mm thin-wall spark plug socket, 6-inch extension, and 3/8-inch ratchet to loosen one spark plug counterclockwise.
• Once loose, spin it out slowly and lift it out with the spark plug socket.
• Remove only one plug at a time so the open hole is exposed for the shortest time possible.
• If a plug feels stuck, stop and work it back and forth gently; do not force it.

Step 6: Check the New Spark Plug Gap

• Use a spark plug gap gauge to carefully verify the gap on each new plug.
• The typical gap for this Honda turbo spark plug application is about 0.7-0.8 mm (0.028-0.031 in).
• Do not pry hard on iridium plug tips; they are delicate and usually come pre-gapped.
• Do not apply anti-seize unless the spark plug manufacturer specifically says to use it.

Step 7: Install the New Spark Plugs by Hand

• Place one new spark plug into the 14mm thin-wall spark plug socket.
• Use only the 6-inch extension by hand to start threading the plug clockwise.
• Turn it several full turns by hand before using a ratchet or torque wrench.
• If it does not turn smoothly, remove it and start again.
• Hand-starting prevents expensive thread damage.

Step 8: Torque the New Spark Plugs

• Attach the 3/8-inch torque wrench to the 6-inch extension and 14mm thin-wall spark plug socket.
• Tighten each spark plug to Torque to 18 Nm (13 ft-lbs).
• Do not over-tighten. The cylinder head is aluminum and can be damaged.

Step 9: Reinstall the Ignition Coils

• Apply a small dab of dielectric grease inside the rubber boot of each ignition coil. Dielectric grease helps seal out moisture but does not conduct electricity.
• Push each ignition coil straight down over its spark plug until it seats fully.
• Use the 10mm socket, 3/8-inch ratchet, and 6-inch extension to install the coil bolts.
• Tighten the ignition coil bolts to Torque to 12 Nm (9 ft-lbs).

Step 10: Reconnect the Coil Connectors and Battery

• Push each ignition coil connector on until it clicks.
• Use the battery terminal wrench 10mm to reconnect the negative battery cable.
• Tighten the battery terminal snugly; do not crush the terminal.
• Reinstall the engine cover by pressing it straight down onto its rubber grommets.

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✅ After Repair

• Start your Civic and let it idle for one to two minutes.
• Listen for smooth idle and make sure there is no shaking or flashing check engine light.
• If the engine misfires, turn it off and recheck that all four ignition coil connectors are fully clicked in.
• Take a short test drive and confirm normal acceleration.
• After disconnecting the battery, some idle relearn may happen automatically as you drive.

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💰 DIY vs Shop Cost

Shop Cost: $220-$420 (parts + labor)

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

You Save: $160-$280 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.8-1.2 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.