🔧 Altima - Spark Plug Replacement

Replacing the spark plugs on your Altima helps restore smooth starts, strong acceleration, and good fuel economy. On the V6 engine, the front bank is straightforward, but the rear bank requires removing the upper intake manifold, so take your time and keep bolts organized.

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

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⚠️ Safety & Precautions

• ⚠️ Let the engine cool completely before starting; hot aluminum threads in the cylinder head can be damaged.
• ⚠️ Disconnect the negative battery cable before unplugging ignition coils or intake sensors.
• ⚠️ Keep dirt, bolts, and tools out of the intake openings. Anything dropped inside can damage the engine.
• ⚠️ Do not use anti-seize on modern plated spark plug threads unless the plug maker specifically requires it; it can cause over-tightening.
• ⚠️ Replace the upper intake manifold gaskets after removal to prevent vacuum leaks.

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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
• 3 inch extension
• 6 inch extension
• 3/8 inch universal joint
• Flat blade screwdriver
• Needle-nose pliers
• Plastic trim clip remover
• Spark plug gap gauge
• Compressed air blower
• Clean shop towels
• Painter’s 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

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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 for at least 1 hour before removing spark plugs.
• 🔋 Use a 10mm socket to disconnect the negative battery cable and move it aside so it cannot touch the battery post.
• 🏷️ Use painter’s tape and a permanent marker to label hoses and electrical connectors before unplugging them.
• 🧰 A spark plug socket has a rubber insert or magnet that holds the plug so you can lift it out safely.
• 🧰 A universal joint is a small swivel adapter that helps your ratchet reach angled bolts.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the Engine Cover

• Use a 10mm socket to remove the engine cover fasteners, if equipped.
• Lift the cover straight up and set it aside.
• Keep bolts in labeled cups.

Step 2: Remove the Air Intake Tube

• Use a flat blade screwdriver to loosen the hose clamp at the throttle body.
• Use a flat blade screwdriver to loosen the hose clamp at the air filter housing.
• Use needle-nose pliers to release any small breather hose clamps, then slide the hoses off carefully.
• Unplug the mass airflow sensor connector by pressing the lock tab and pulling straight back.
• Remove the intake tube and place a clean shop towel over the throttle body opening.

Step 3: Remove Front Bank Ignition Coils

• The ignition coil is the small electrical unit sitting directly on top of each spark plug.
• Use painter’s tape and a permanent marker to label the front three ignition coil connectors.
• Press the connector tab and unplug each ignition coil connector by hand.
• Use a 10mm socket to remove the ignition coil retaining bolt from each front coil.
• Twist each coil gently by hand, then pull it straight out.

Step 4: Clean the Front Spark Plug Wells

• Use a compressed air blower to blow dirt away from each spark plug well.
• Wear safety glasses while using compressed air.
• Dirt in the cylinder can scratch metal.

Step 5: Remove Front Spark Plugs

• Use a 5/8 inch spark plug socket, 6 inch extension, and 3/8 inch drive ratchet to loosen each front spark plug.
• Turn counterclockwise slowly until the plug is free.
• Lift the spark plug out with the spark plug socket.
• If a plug feels stuck, tighten it slightly, then loosen again gently.

Step 6: Install Front Spark Plugs

• Use a spark plug gap gauge to verify the new spark plug gap is about 0.043 in.
• Place the new spark plug into the 5/8 inch spark plug socket.
• Use the 6 inch extension by hand only to start the spark plug threads.
• Turn clockwise by hand until the plug seats. This prevents cross-threading.
• Use a 3/8 inch drive torque wrench and 5/8 inch spark plug socket to tighten each spark plug to Torque to 19.6 Nm (14 ft-lbs).

Step 7: Reinstall Front Ignition Coils

• Push each ignition coil straight down over its spark plug by hand.
• Use a 10mm socket to install each ignition coil bolt.
• Tighten each ignition coil bolt to Torque to 5.4 Nm (48 in-lbs).
• Plug each ignition coil connector back in until it clicks.

Step 8: Prepare to Remove the Upper Intake Manifold

• The upper intake manifold is the large aluminum air chamber on top of the rear spark plugs.
• Use painter’s tape and a permanent marker to label vacuum hoses and electrical connectors attached to the manifold and throttle body area.
• Use needle-nose pliers to loosen hose clamps, then slide vacuum hoses off carefully.
• Use a 10mm socket to remove brackets or small harness retainers attached to the intake manifold.
• Use a clean shop towel to catch any small bolts so they do not fall behind the engine.

Step 9: Remove the Throttle Body from the Upper Intake Manifold

• Unplug the throttle body electrical connector by pressing the lock tab and pulling straight back.
• Use a 10mm socket to remove the throttle body bolts.
• Move the throttle body aside without pulling hard on hoses or wiring.
• Remove and discard the old throttle body gasket.
• Do not spray cleaner into electronics.

Step 10: Remove the Upper Intake Manifold

• Use a 12mm socket, 3 inch extension, 6 inch extension, and 3/8 inch ratchet to remove the upper intake manifold bolts and support bolts.
• Use a 3/8 inch universal joint where access is angled near the rear of the engine.
• Lift the upper intake manifold straight up and out.
• Immediately cover the open lower intake ports with clean shop towels.
• Remove and discard the old upper intake manifold gaskets.

Step 11: Remove Rear Bank Ignition Coils

• Use painter’s tape and a permanent marker to label the rear three ignition coil connectors.
• Press each connector tab and unplug the connector by hand.
• Use a 10mm socket to remove each rear ignition coil bolt.
• Twist each coil gently by hand, then pull it straight out.

Step 12: Clean the Rear Spark Plug Wells

• Use a compressed air blower to clear dirt from each rear spark plug well.
• Wear safety glasses while blowing out the wells.
• Check that no loose gasket pieces or debris are near the intake openings.

Step 13: Remove Rear Spark Plugs

• Use a 5/8 inch spark plug socket, 6 inch extension, 3/8 inch universal joint, and 3/8 inch drive ratchet to loosen each rear spark plug.
• Turn counterclockwise slowly until the plug is free.
• Lift each spark plug out carefully with the spark plug socket.

Step 14: Install Rear Spark Plugs

• Use a spark plug gap gauge to verify the new spark plug gap is about 0.043 in.
• Place each new spark plug into the 5/8 inch spark plug socket.
• Use the 6 inch extension by hand only to start each plug.
• Use a 3/8 inch drive torque wrench, 5/8 inch spark plug socket, and 3/8 inch universal joint if needed.
• Tighten each rear spark plug to Torque to 19.6 Nm (14 ft-lbs).

Step 15: Reinstall Rear Ignition Coils

• Push each rear ignition coil straight down until fully seated.
• Use a 10mm socket to install each ignition coil bolt.
• Tighten each ignition coil bolt to Torque to 5.4 Nm (48 in-lbs).
• Reconnect each ignition coil connector until it clicks.

Step 16: Install New Upper Intake Manifold Gaskets

• Use clean shop towels to wipe the gasket sealing surfaces gently.
• Remove the shop towels from the lower intake ports only after the area is clean.
• Install the new upper intake manifold gaskets into position by hand.
• Make sure each gasket sits flat and is not twisted.

Step 17: Reinstall the Upper Intake Manifold

• Set the upper intake manifold straight down onto the new gaskets.
• Use a 12mm socket and extension to start all manifold bolts by hand before tightening.
• Use a 3/8 inch drive torque wrench to tighten the upper intake manifold bolts evenly in a crisscross pattern.
• Tighten the upper intake manifold bolts to Torque to 24.5 Nm (18 ft-lbs).
• Use a 10mm socket to reinstall any small brackets and harness retainers removed earlier.

Step 18: Reinstall the Throttle Body

• Install the new throttle body gasket by hand.
• Position the throttle body onto the intake manifold.
• Use a 10mm socket to start all throttle body bolts by hand.
• Use a 3/8 inch drive torque wrench to tighten the throttle body bolts to Torque to 8.8 Nm (78 in-lbs).
• Reconnect the throttle body electrical connector until it clicks.

Step 19: Reconnect Hoses, Connectors, and Intake Tube

• Use your tape labels to reconnect all vacuum hoses and electrical connectors.
• Use needle-nose pliers to reinstall spring clamps on hoses.
• Reinstall the air intake tube onto the throttle body and air filter housing.
• Use a flat blade screwdriver to tighten both intake tube clamps snugly.
• Reconnect the mass airflow sensor connector until it clicks.

Step 20: Reconnect Battery and Reinstall Engine Cover

• Use a 10mm socket to reconnect the negative battery cable.
• Use a 10mm socket to reinstall the engine cover fasteners, if equipped.
• Check the engine bay for leftover tools, towels, and loose connectors.

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✅ After Repair

• ✅ Start your Altima and let it idle for a few minutes.
• 👂 Listen for hissing sounds, which can mean a vacuum hose or intake gasket is leaking.
• ⚠️ If the idle is rough, shut the engine off and recheck every ignition coil connector, vacuum hose, and intake tube clamp.
• 🚗 Take a short test drive after the idle smooths out.
• 🔍 Recheck for warning lights after the test drive.
• 📌 If the idle speed acts unusual after battery disconnect, let the engine idle with all accessories off for several minutes so the throttle can relearn.

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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 2.0-3.0 hours.

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