🔧 Altima - Spark Plug Replacement

Replacing the spark plugs on your Altima helps restore smooth idle, clean acceleration, and proper fuel economy. The 2.5L engine uses four ignition coils on top of the engine, with one spark plug underneath each coil.

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

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⚠️ Safety & Precautions

• ⚠️ Let the engine cool completely before starting; the aluminum cylinder head can be damaged if spark plugs are removed hot.
• ⚠️ Disconnect the negative battery cable to reduce the chance of accidental short circuits.
• ⚠️ Keep dirt and debris out of the spark plug wells; anything that falls in can enter the engine.
• ⚠️ Do not over-tighten spark plugs; the cylinder head threads are aluminum and can strip.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 14mm spark plug socket
• 3/8-inch drive ratchet
• 3/8-inch drive 6-inch extension
• 3/8-inch drive torque wrench
• Flathead screwdriver
• Compressed air blow gun
• Dielectric grease packet
• Anti-seize compound packet
• Needle-nose pliers
• Battery terminal wrench 10mm
• Safety glasses
• Nitrile gloves

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs - Qty: 4

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📋 Before You Begin

• Park your Altima on level ground and set the parking brake.
• Open the hood and let the engine cool until it is safe to touch.
• Disconnect the negative battery cable using a 10mm battery terminal wrench.
• A spark plug socket is a deep socket with a rubber insert or magnet that holds the spark plug while you remove and install it.
• A torque wrench is a tool that tightens bolts or spark plugs to the correct tightness so parts are not damaged.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the Engine Cover

• Use both hands to gently lift the plastic engine cover straight upward.
• If it feels stuck, lift one corner at a time by hand until the rubber mounts release.
• Set the cover aside where it will not get scratched or stepped on.
• Pull upward, not sideways.

Step 2: Locate the Ignition Coils

• Look across the top of the engine for four ignition coils.
• Each ignition coil has an electrical connector and one 10mm retaining bolt.
• An ignition coil is the small electrical part that sends spark to one spark plug.

Step 3: Disconnect the First Ignition Coil Connector

• Use a flathead screwdriver to gently lift the connector lock tab if needed.
• Press the release tab with your finger and pull the connector straight off the coil.
• If the connector is tight, use needle-nose pliers carefully on the connector body, not the wires.
• Never pull on wiring.

Step 4: Remove the First Ignition Coil

• Use a 10mm socket, 3/8-inch drive ratchet, and 3/8-inch drive 6-inch extension to remove the ignition coil bolt.
• Twist the ignition coil gently by hand to loosen the rubber boot.
• Pull the ignition coil straight upward and set it aside in order.
• When reinstalling later, tighten the ignition coil bolt to Torque to 5 Nm (44 in-lbs).

Step 5: Clean the Spark Plug Well

• Put on safety glasses.
• Use a compressed air blow gun to blow dirt out of the spark plug well.
• The spark plug well is the deep tube where the spark plug sits.
• Clean before removing the plug.

Step 6: Remove the Old Spark Plug

• Place the 14mm spark plug socket onto the 3/8-inch drive 6-inch extension and 3/8-inch drive ratchet.
• Lower the socket straight down onto the spark plug.
• Turn counterclockwise slowly until the spark plug is fully loose.
• Lift the spark plug out carefully using the 14mm spark plug socket.
• If it feels very tight, stop and tighten it slightly, then loosen again slowly.

Step 7: Prepare the New Spark Plug

• Compare the new iridium spark plug to the old one to confirm the same length and thread size.
• Do not bend or adjust the tip unless the plug manufacturer specifically says to check gap.
• Apply a very small amount of anti-seize compound packet only if the spark plug manufacturer does not already coat the threads.
• Keep anti-seize away from the electrode tip.
• Less is better here.

Step 8: Install the New Spark Plug by Hand

• Place the new spark plug into the 14mm spark plug socket.
• Lower it straight into the spark plug well using the 3/8-inch drive 6-inch extension.
• Turn the extension by hand clockwise for several turns.
• If it does not turn easily by hand, remove it and start again.
• Cross-threading means the plug is going in crooked and can damage the engine threads.

Step 9: Torque the New Spark Plug

• Attach the 3/8-inch drive torque wrench to the 14mm spark plug socket and 3/8-inch drive 6-inch extension.
• Tighten the spark plug to Torque to 18 Nm (13 ft-lbs).
• Stop as soon as the torque wrench clicks.
• Do not add extra tightening.

Step 10: Reinstall the Ignition Coil

• Apply a small dab of dielectric grease packet inside the end of the ignition coil boot.
• Dielectric grease helps seal out moisture but does not repair damaged parts.
• Push the ignition coil straight down onto the new spark plug until seated.
• Install the coil bolt using a 10mm socket, 3/8-inch drive ratchet, and 3/8-inch drive torque wrench.
• Tighten the ignition coil bolt to Torque to 5 Nm (44 in-lbs).
• Reconnect the electrical connector until it clicks.

Step 11: Repeat for the Other Three Spark Plugs

• Repeat Steps 3 through 10 for the remaining three ignition coils and spark plugs.
• Use the 10mm socket for each coil bolt.
• Use the 14mm spark plug socket, 3/8-inch drive 6-inch extension, and 3/8-inch drive torque wrench for each spark plug.
• Keep the coils in the same positions unless you are replacing them.

Step 12: Reinstall the Engine Cover

• Line up the engine cover with the mounting posts by hand.
• Press down firmly over each mounting point until the cover seats.
• Reconnect the negative battery cable using a 10mm battery terminal wrench.
• Tighten the battery terminal snugly; do not crush the terminal.

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✅ After Repair

• ✅ Start the engine and let it idle for one minute.
• ✅ Listen for smooth idle and confirm there are no warning lights flashing.
• ✅ If the engine misfires or runs rough, shut it off and recheck that all four coil connectors are fully clicked in.
• ✅ Take a short test drive and confirm normal acceleration.
• ✅ If the battery was disconnected, reset the clock and any one-touch window function if needed.

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💰 DIY vs Shop Cost

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

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

You Save: $130-$330 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1-2 hours.

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🎯 Ready to get started?

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