🔧 Altima - Spark Plug Replacement

Your Altima’s spark plugs sit under the ignition coils on top of the engine. Replacing them restores smooth starting, idle quality, and fuel economy, especially if you’re due by mileage or have a misfire.

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

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⚠️ Safety & Precautions

• ⚠️ Let the engine cool fully before starting (hot aluminum threads can strip).
• ⚠️ Hybrid safety: keep hands/tools away from any orange high-voltage cables and connectors.
• ⚠️ Turn ignition OFF and keep the key/fob away from the car so the system can’t power up.
• ⚠️ If you choose to disconnect power, disconnect the 12V battery negative terminal first.
• ⚠️ Do not use anti-seize on new plugs (can cause over-torque).

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 3/8" drive ratchet
• 3/8" drive torque wrench (10–40 ft-lbs range)
• 5/8" spark plug socket (rubber insert)
• 6" socket extension
• 12" socket extension
• Small flathead screwdriver
• Compressed air blow gun
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs (OEM-spec) - Qty: 4
• Dielectric grease - Qty: 1

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📋 Before You Begin

• Park on level ground and set the parking brake.
• Open the hood and confirm the engine is completely cool to the touch.
• If disconnecting the 12V battery: use a 10mm socket to remove the negative terminal and isolate it so it can’t spring back.
• Have your new plugs ready; iridium plugs are fragile—don’t drop them and don’t “gap” them (bend the tip).

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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 to remove any cover fasteners, then lift the cover off.

Step 2: Unplug ignition coil connectors

• Locate the four ignition coils on top of the valve cover (one per cylinder).
• Use a small flathead screwdriver to gently lift the connector lock tab if needed, then pull the connector straight off.
• Tip: Pull on the connector, not the wires.

Step 3: Remove the ignition coils

• Use a 10mm socket to remove the bolt holding each coil.
• Twist the coil slightly and pull straight up to remove it.
• Set coils aside in order (so each coil can return to the same cylinder if you’re reusing them).
• When reinstalling coil bolts: Torque to 10 Nm (7 ft-lbs).

Step 4: Clean the spark plug wells

• Use compressed air blow gun to blow out dirt/debris from each spark plug tube before removing the plug.
• This helps prevent debris from falling into the cylinder.

Step 5: Remove the old spark plugs

• Install the 5/8" spark plug socket (rubber insert) onto a 6" socket extension (add the 12" socket extension if needed for reach).
• Use the 3/8" drive ratchet to loosen each plug counterclockwise, then remove it.
• If a plug feels stuck, stop and work it out slowly to avoid damaging threads.

Step 6: Install the new spark plugs

• Confirm the new plugs match the old ones (same length and seat type).
• Start each plug by hand first using the spark plug socket and extension (no ratchet at first) to avoid cross-threading.
• Once finger-tight, use the 3/8" drive torque wrench to tighten: Torque to 25 Nm (18 ft-lbs).
• Do not over-tighten—this can strip the cylinder head.

Step 7: Reinstall ignition coils

• Put a tiny amount of dielectric grease inside each coil boot (the rubber spark plug “cup”).
• Push each coil straight down until fully seated on the plug.
• Install coil bolts with a 10mm socket, then Torque to 10 Nm (7 ft-lbs) using the torque wrench.

Step 8: Reconnect coil connectors and reinstall cover

• Reconnect each coil electrical connector until it clicks in place.
• Reinstall the engine cover using a 10mm socket.
• If you disconnected the 12V battery, reconnect the negative terminal using a 10mm socket.

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✅ After Repair

• Start your Altima and let it idle for 1–2 minutes. It should run smooth with no shaking.
• Listen for any ticking (a sign a coil may not be seated) and re-check connectors if needed.
• If the check engine light was on for a misfire, you may need a scan tool to clear codes after confirming the fix.
• Take a short test drive and confirm normal power and no warning lights.

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💰 DIY vs Shop Cost

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

DIY Cost: $45-$120 (parts only)

You Save: $130-$405 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.