🔧 Altima - Spark Plug Replacement

On your Altima, the spark plugs sit under the ignition coils on top of the engine. Replacing them helps prevent misfires, rough idle, poor fuel economy, and hard starting.

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 protect the aluminum cylinder head threads.
• ⚠️ Disconnect the negative battery terminal to avoid accidental shorts while unplugging coils.
• ⚠️ Do not over-tighten spark plugs—stripped threads are a big repair.
• ⚠️ Keep dirt out of the spark plug holes; debris can damage the engine.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• 10mm socket
• 3/8" drive ratchet
• 3/8" drive extension set (3" and 6")
• 5/8" spark plug socket (rubber insert)
• Torque wrench (3/8" drive, 10-30 ft-lbs range)
• Flathead screwdriver
• Trim clip tool
• Compressed air blow gun
• Feeler gauge (0.043" / 1.1 mm)
• Dielectric grease

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (iridium, OEM-equivalent) - Qty: 4
• Ignition coil boot (optional, if boots are torn or oil-soaked) - Qty: 4
• PCV valve (optional, if doing tune-up bundle) - Qty: 1

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📋 Before You Begin

• Park on level ground, set the parking brake, and let the engine cool fully.
• Open the hood and keep loose clothing/hair away from belts and fans.
• Use a 10mm socket to disconnect the negative battery terminal and move it aside so it can’t spring back.
• Label coils 1-4 if you’re nervous.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover (if equipped)

• Use a 10mm socket and 3/8" ratchet to remove the engine cover fasteners.
• Lift the cover off and set it aside.

Step 2: Move any intake ducting that blocks access (if needed)

• Use a flathead screwdriver to loosen hose clamps on the intake duct if it blocks the coil area.
• Use a trim clip tool to pop any plastic clips holding ducts/wiring retainers.
• Shift the ducting aside without yanking on connectors.

Step 3: Unplug the ignition coils

• Each spark plug has an ignition coil on top (the coil makes the spark).
• Press the electrical connector tab and pull the connector off each coil by hand.
• If a connector is stuck, use a trim clip tool gently—don’t pry hard.

Step 4: Remove the ignition coils

• Use a 10mm socket with a 3/8" ratchet to remove the coil hold-down bolt for cylinder 1.
• Twist the coil slightly, then pull it straight up and out.
• Repeat for all 4 coils.
• Keep coils in order to troubleshoot later.

Step 5: Clean out the spark plug wells

• Before removing plugs, use compressed air blow gun to blow dirt out of each spark plug hole area.
• This helps prevent debris from falling into the cylinder.

Step 6: Remove the old spark plugs

• Use a 5/8" spark plug socket (rubber insert) with a 3/8" extension and ratchet.
• Turn counterclockwise to loosen, then remove the plug carefully.
• If a plug feels extremely tight, stop and work it slowly to avoid thread damage.

Step 7: Check and prep the new spark plugs

• Use a feeler gauge (0.043" / 1.1 mm) to verify the gap (the “gap” is the space the spark jumps across).
• If you’re using OEM-style iridium plugs, they’re typically pre-gapped—don’t bend the tiny center tip.
• Put a small smear of dielectric grease inside each coil boot (this helps prevent moisture and makes removal easier).
• Skip anti-seize unless your plug maker requires it.

Step 8: Install the new spark plugs (by hand first)

• Place the new plug into the 5/8" spark plug socket and lower it into the hole using a 3/8" extension.
• Thread the plug in by hand using just the extension (no ratchet at first) to avoid cross-threading.
• Once it seats, use a torque wrench to tighten.
• Torque to 25 Nm (18 ft-lbs).
• Repeat for all 4 cylinders.

Step 9: Reinstall coils and connectors

• Push each coil straight down onto its spark plug until it fully seats.
• Install the coil hold-down bolt using a 10mm socket and 3/8" ratchet.
• Torque to 10 Nm (7 ft-lbs).
• Reconnect each coil electrical connector until it clicks.

Step 10: Reassemble and reconnect battery

• Reinstall any intake ducting using a flathead screwdriver for clamps and a trim clip tool for clips.
• Reinstall the engine cover using a 10mm socket.
• Reconnect the negative battery 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.
• Listen for ticking/air leaks around the intake ducting you moved.
• If you get a check engine light or rough running, re-check coil connectors and make sure each coil is fully seated.
• Test drive gently for 10 minutes.

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💰 DIY vs Shop Cost

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

DIY Cost: $35-$90 (parts only)

You Save: $160-$360 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?

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.