🔧 Altima - Spark Plug Replacement

Replacing the spark plugs on your Altima helps restore smooth starts, strong acceleration, and proper fuel economy. On the V6, the rear bank plugs sit under the upper intake manifold, so this job is more involved than a basic 4-cylinder spark plug change.

Difficulty Level: Intermediate | Estimated Time: 2.5-4 hours

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⚠️ Safety & Precautions

• ⚠️ Work only on a completely cool engine to avoid burns and damaged aluminum threads.
• ⚠️ Disconnect the negative battery cable before unplugging ignition coils and throttle body connectors.
• ⚠️ Do not drop anything into the intake ports once the intake manifold is removed.
• ⚠️ Do not use anti-seize on the new spark plugs unless the plug manufacturer specifically requires it; most modern plugs are coated.
• ⚠️ Start each spark plug by hand first. Cross-threading means the plug goes in crooked and can damage the cylinder head.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 12mm socket
• 14mm socket
• 5/8-inch spark plug socket
• 3/8-inch drive ratchet
• 3/8-inch drive torque wrench
• 6-inch extension
• 3-inch extension
• Universal joint adapter
• Flathead screwdriver
• Needle-nose pliers
• Plastic trim removal tool
• Spark plug gap gauge
• Compressed air blow gun
• Clean shop towels
• Masking tape
• Permanent marker
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs - Qty: 6
• Upper intake manifold gasket set - Qty: 1
• Throttle body gasket - Qty: 1
• Dielectric grease - Qty: 1 small tube
• Mass airflow sensor-safe intake cleaner - Qty: 1 can

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📋 Before You Begin

• Park your Altima on level ground, shift to Park, and set the parking brake.
• Let the engine cool fully. Aluminum cylinder heads are easier to damage when hot.
• Open the hood and remove the key from the vehicle.
• Use a 10mm socket to disconnect the negative battery cable. Move the cable so it cannot spring back to the terminal.
• Use masking tape and a permanent marker to label hoses and electrical connectors as you remove them. This helps a first-time DIYer avoid mix-ups.
• A torque wrench is a tool that tightens bolts to an exact tightness so parts are not damaged.
• A spark plug socket is a deep socket with a rubber insert or magnet that holds the plug while you remove or install it.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the Engine Cover

• Use your hands and a plastic trim removal tool to lift the plastic engine cover upward from its mounting grommets.
• Set the cover aside where it will not get scratched or stepped on.
• Pull straight up gently.

Step 2: Disconnect the Air Intake Duct

• Use a flathead screwdriver to loosen the clamp at the throttle body.
• Use a flathead screwdriver to loosen the clamp at the air cleaner box.
• Use needle-nose pliers to release any small hose clamps attached to the intake duct.
• Remove the intake duct and set it aside.

Step 3: Unplug the Throttle Body and Move Hoses Aside

• Press the lock tab and unplug the throttle body electrical connector by hand.
• Use needle-nose pliers to release nearby vacuum hose clamps.
• Label each hose with masking tape and a permanent marker before removal.
• Move the hoses aside without pulling hard on them.

Step 4: Remove the Upper Intake Manifold

• Use a 10mm socket, 12mm socket, ratchet, and extension to remove the upper intake manifold bolts and brackets.
• Use a 14mm socket if equipped for the rear support bracket fasteners.
• Lift the upper intake manifold carefully from the engine.
• Place clean shop towels into the open intake ports immediately so nothing can fall inside.
• Remove the old upper intake manifold gaskets by hand.
• Take photos before unplugging connectors.

Step 5: Remove the Front Ignition Coils

• Use a 10mm socket to remove the ignition coil hold-down bolt from each front coil.
• Press the connector tab and unplug each ignition coil by hand.
• Twist each coil slightly, then pull it straight upward.
• Set the coils in order so they go back to the same cylinders.

Step 6: Remove the Rear Ignition Coils

• With the intake manifold removed, use a 10mm socket, ratchet, and 3-inch extension to remove the rear ignition coil bolts.
• Unplug each rear ignition coil connector by hand.
• Twist each coil slightly, then pull it straight upward.
• Keep each coil in order on a clean towel.

Step 7: Blow Dirt Out of the Spark Plug Wells

• Put on safety glasses before using compressed air.
• Use a compressed air blow gun to clean dirt and grit from each spark plug well.
• This step prevents debris from falling into the engine when the plugs come out.

Step 8: Remove the Old Spark Plugs

• Use a 5/8-inch spark plug socket, 6-inch extension, universal joint adapter, and 3/8-inch ratchet to loosen each spark plug.
• Turn counterclockwise slowly until the plug comes free.
• Lift the spark plug out using the spark plug socket.
• If a plug feels stuck, tighten it slightly, then loosen again gently. Do not force it.

Step 9: Check the New Spark Plugs

• Use a spark plug gap gauge to verify the new plugs are correctly gapped to 0.043 in / 1.1 mm.
• Do not pry against the fine iridium center electrode.
• Inspect each plug for cracked porcelain or shipping damage.

Step 10: Install the New Spark Plugs

• Place one new spark plug into the 5/8-inch spark plug socket.
• Use the extension by hand only to start threading the plug clockwise.
• After the plug is fully hand-started, use a 3/8-inch drive torque wrench with the 5/8-inch spark plug socket.
• Torque to 25 Nm (18 ft-lbs).
• Repeat for all six spark plugs.
• Hand-start every plug first.

Step 11: Reinstall the Ignition Coils

• Apply a tiny amount of dielectric grease inside each ignition coil boot. Dielectric grease helps seal moisture out of electrical boots.
• Push each ignition coil straight down onto its matching spark plug.
• Use a 10mm socket to install each ignition coil bolt.
• Torque to 7 Nm (62 in-lbs).
• Reconnect each ignition coil electrical connector by hand until it clicks.

Step 12: Reinstall the Upper Intake Manifold

• Remove the clean shop towels from the intake ports.
• Install the new upper intake manifold gaskets by hand.
• Carefully lower the intake manifold into place.
• Use a 10mm socket and torque wrench to tighten the intake manifold bolts evenly in several passes.
• Torque to 25 Nm (18 ft-lbs).
• Use a 12mm socket or 14mm socket to reinstall any support brackets removed earlier.
• Torque support bracket bolts to 25 Nm (18 ft-lbs).

Step 13: Reinstall the Throttle Body and Intake Duct

• If the throttle body was removed, install a new throttle body gasket by hand.
• Use a 10mm socket to install the throttle body bolts.
• Torque to 8 Nm (71 in-lbs).
• Reconnect the throttle body electrical connector by hand until it clicks.
• Use needle-nose pliers to reinstall hose clamps.
• Use a flathead screwdriver to tighten the air intake duct clamps.

Step 14: Reconnect the Battery

• Use a 10mm socket to reconnect the negative battery cable.
• Torque to 5 Nm (44 in-lbs).
• Make sure the terminal is snug and does not rotate by hand.

Step 15: Reinstall the Engine Cover

• Use your hands to line up the engine cover with the rubber grommets.
• Press straight down until it seats securely.

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✅ After Repair

• Start your Altima and let it idle. It may crank slightly longer the first time.
• Listen for vacuum leaks. A vacuum leak often sounds like a steady hiss near the intake manifold.
• Watch for a rough idle or check engine light. If either happens, recheck coil connectors, hose connections, and intake duct clamps.
• Let the engine idle for several minutes so the electronic throttle can stabilize.
• Take a short test drive and confirm smooth acceleration with no misfire or hesitation.

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💰 DIY vs Shop Cost

Shop Cost: $450-$750 (parts + labor)

DIY Cost: $90-$180 (parts only)

You Save: $270-$660 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2-3 hours.

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🎯 Ready to get started?

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