🔧 Altima - Spark Plug Replacement

On your Altima, the spark plugs fire the air/fuel mixture. Worn plugs can cause rough idle, misfires, poor fuel economy, and hard starts. This job is straightforward because the plugs sit under the ignition coils on top of the engine.

Difficulty Level: Intermediate | Estimated Time: 1.0-2.0 hours

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⚠️ Safety & Precautions

• ⚠️ Work on a cold engine to avoid burns and to prevent thread damage in the aluminum cylinder head.
• ⚠️ Disconnect the negative battery cable to prevent accidental shorts when unplugging ignition coils.
• ⚠️ Blow debris away from each spark plug well before removing plugs so dirt doesn’t fall into the engine.
• ⚠️ Do not over-tighten spark plugs; the cylinder head is aluminum and threads can strip.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 3/8" drive ratchet
• 3/8" drive extension set (3" and 6")
• 16mm spark plug socket (5/8")
• Torque wrench (3/8" drive, 10–30 Nm range)
• Flat-blade screwdriver
• Compressed air blow gun
• Clean shop towels
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (iridium, OEM-equivalent) - 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 (at least 1 hour if it was running).
• Open the hood and disconnect the battery negative terminal using a 10mm socket.
• Label connectors if you’re unsure.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine appearance cover (if equipped)

• Pull up on the cover to release the rubber grommets, or remove any fasteners using a 10mm socket (varies by cover style).
• Set the cover aside.

Step 2: Unplug and remove ignition coils (one cylinder at a time)

• Locate the four ignition coils on top of the valve cover.
• Release each electrical connector lock using a flat-blade screwdriver, then pull the connector straight off.
• Remove the coil retaining bolt using a 10mm socket.
• Twist the coil slightly and pull it straight up to remove it.
• Reinstall spec later: Torque to 7.2 Nm (64 in-lbs).

Step 3: Clean the spark plug wells

• Use a compressed air blow gun to blow out dirt around the spark plug hole.
• Wipe the area with clean shop towels.
• Clean wells prevent engine damage.

Step 4: Remove the old spark plugs

• Install a 16mm spark plug socket (5/8") on a 3/8" drive extension set (3" and 6") and a 3/8" drive ratchet.
• Turn counterclockwise to loosen and remove the spark plug.
• If it feels stuck, stop and work it slowly back-and-forth with the 3/8" drive ratchet.

Step 5: Check and install the new spark plugs

• Verify the new plugs match the old ones in length and seat type.
• Start the new plug by hand using the 16mm spark plug socket (5/8") and 3/8" drive extension set (3" and 6") only (no ratchet at first) to avoid cross-threading.
• Once seated, tighten with a torque wrench (3/8" drive, 10–30 Nm range) to 18 Nm (13 ft-lbs).
• A torque wrench applies exact tightness.

Step 6: Reinstall ignition coils

• Apply a very small amount of dielectric grease inside the coil boot (the rubber end) if desired.
• Push the coil straight down onto the spark plug until fully seated.
• Install the coil bolt using a 10mm socket, then tighten to 7.2 Nm (64 in-lbs) using the torque wrench (3/8" drive, 10–30 Nm range).
• Reconnect the coil electrical connector until it clicks.
• Repeat Steps 2–6 for the remaining cylinders.

Step 7: Reassemble and reconnect the battery

• Reinstall the engine cover (if equipped) by pressing it back onto the grommets.
• Reconnect the battery negative 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 with no shaking.
• Check that the Check Engine Light stays off.
• If it runs rough, recheck that each coil connector is fully clicked in and each coil is seated.
• Road test for 10 minutes and recheck for any warning lights.

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💰 DIY vs Shop Cost

Shop Cost: $250-$450 (parts + labor)

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

You Save: $130-$400 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.0-2.0 hours.

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🎯 Ready to get started?

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