🔧 Altima - Spark Plug Replacement

Your Altima’s spark plugs ignite the air/fuel mix. Worn plugs can cause rough idle, poor fuel economy, and misfires. This job is straightforward because the plugs sit on top of the engine under the ignition coils.

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 prevent thread damage in the cylinder head.
• ⚠️ Disconnect the negative battery cable if you’re worried about accidentally shorting connectors.
• ⚠️ Keep dirt out of the spark plug holes—debris can fall into the engine.
• ⚠️ Do not over-tighten spark plugs (aluminum head threads can strip).

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 3/8" ratchet
• 3/8" extension set (3" and 6")
• 14mm thin-wall spark plug socket
• Torque wrench (3/8")
• Flat trim tool
• Compressed air blow gun
• Shop light
• 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

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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 after driving).
• If disconnecting the battery: use a 10mm socket to remove the negative cable and isolate it so it can’t spring back.
• Blow off loose dust around the top of the engine using compressed air blow gun.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine appearance cover

• Pull up carefully on the cover to pop it off its grommets (use a flat trim tool if it’s stubborn).
• Set the cover aside.

Step 2: Unplug the ignition coil electrical connectors

• Locate the 4 ignition coils on top of the engine (one per spark plug).
• Press the connector lock tab and pull the connector straight back by hand. If needed, gently help the tab with a flat trim tool.
• Do one coil at a time to stay organized.

Step 3: Remove the ignition coils

• Use a 10mm socket with a 3/8" ratchet to remove the coil hold-down bolt.
• Twist the coil slightly, then pull it straight up to remove it.
• Repeat for each coil.
• When reinstalling coil bolts later: Torque to 10 Nm (89 in-lbs).

Step 4: Clean around the spark plug wells

• Blow out each spark plug tube using the compressed air blow gun so no debris falls into the cylinder.
• Use your shop light to verify the area is clean.

Step 5: Remove the old spark plugs

• Install the 14mm thin-wall spark plug socket on a 3/8" extension (6") and 3/8" ratchet.
• Turn counterclockwise to loosen, then remove the plug fully.
• Repeat for all 4 cylinders.

Step 6: Install the new spark plugs

• Check each new plug matches the old plug in length/seat style before installing.
• Carefully start each plug by hand using the 14mm thin-wall spark plug socket and extension (no ratchet at first) to avoid cross-threading.
• Once finger-tight, use a torque wrench (3/8") to tighten each plug: Torque to 18 Nm (13 ft-lbs).
• Torque wrench = tool that tightens to a set force.
• Don’t adjust iridium plug gap unless specified.

Step 7: Reinstall ignition coils

• Apply a very small amount of dielectric grease inside each coil boot.
• Push each coil straight down until it seats fully on the plug.
• Install coil bolts using a 10mm socket, then: Torque to 10 Nm (89 in-lbs).

Step 8: Reconnect coil connectors and reinstall the engine cover

• Plug in each coil connector until it clicks (pull gently to confirm it’s locked).
• Reinstall the engine cover by aligning it and pressing down firmly by hand.
• If you disconnected the battery, reconnect it 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.
• If the check engine light comes on or it runs rough, re-check every coil connector is fully clicked in.
• If you disconnected the battery, you may need to re-initialize the auto-up/down windows (hold the window switch down, then up for a few seconds at full travel).
• Test drive 5–10 minutes and confirm no hesitation under light acceleration.

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💰 DIY vs Shop Cost

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

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

You Save: $190-$310 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.0-1.5 hours.

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🎯 Ready to get started?

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