🔧 Altima - Spark Plug Replacement

On your Altima V6, you’re replacing 6 spark plugs (one per cylinder). The front bank is easy to reach, but the rear bank sits under the upper intake manifold, so that must be removed to access the last 3 plugs.

Difficulty Level: Advanced | Estimated Time: 2.5-4.0 hours

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⚠️ Safety & Precautions

• ⚠️ Let the engine cool fully (hot aluminum threads strip easily).
• ⚠️ Disconnect the negative battery cable to prevent accidental shorts.
• ⚠️ Keep dirt out of the intake ports—stuff clean rags in openings immediately.
• ⚠️ Do not over-tighten spark plugs (aluminum cylinder heads are easy to damage).
• ⚠️ If you unplug many connectors, label them with tape to avoid mix-ups.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• 10mm socket
• 12mm socket
• 3/8" drive ratchet
• 3/8" drive torque wrench (10-100 ft-lbs range)
• 5/8" spark plug socket
• 6" extension (3/8" drive)
• 10" extension (3/8" drive)
• Universal swivel joint (3/8" drive)
• Flathead screwdriver
• Needle-nose pliers
• Pick tool
• Shop vacuum
• Clean shop rags

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (iridium, OEM-equivalent) - Qty: 6
• Upper intake manifold gasket set - Qty: 1
• Dielectric grease - Qty: 1

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📋 Before You Begin

• 🅿️ Park on level ground and set the parking brake.
• 🔋 Use a 10mm socket to disconnect the negative battery cable and keep it from springing back.
• 🧼 Use a shop vacuum to clean dirt/leaves around the intake and ignition coils before you open anything.
• 🧻 Have clean shop rags ready to plug intake openings once the upper intake is lifted.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover and intake duct

• Remove the plastic engine cover (if equipped) using a 10mm socket.
• Loosen the air duct clamps using a flathead screwdriver.
• Unplug the intake tube sensor connector(s) (press the tab, pull straight back).
• Lift the intake duct off and set it aside with the clamps still on it.

Step 2: Replace the 3 front-bank spark plugs (radiator-side)

• Unplug each ignition coil connector (press the lock tab, then pull).
• Remove each coil hold-down bolt using a 10mm socket.
• Twist and pull the coil up to remove it. Wiggle—don’t pry hard.
• Before removing a plug, vacuum around the plug well using a shop vacuum.
• Remove the spark plug using a 5/8" spark plug socket, 10" extension, and 3/8" drive ratchet.
• Install the new spark plug by hand first using the 5/8" spark plug socket and extension (no ratchet yet) to avoid cross-threading.
• Tighten using a torque wrench: Torque to 25 Nm (18 ft-lbs).
• Add a small dab of dielectric grease inside the coil boot (this helps prevent moisture/tearing).
• Reinstall coils and bolts using a 10mm socket: Torque to 7 Nm (62 in-lbs).
• Reconnect the coil connectors (you should feel a positive “click”).

Step 3: Remove the upper intake manifold to access the rear bank

• Unplug the throttle body electrical connector and any nearby connectors that prevent lifting the intake (use a pick tool gently if a lock tab is stubborn).
• Disconnect vacuum/PCV hoses from the upper intake using needle-nose pliers for spring clamps (take a quick phone photo first).
• Remove the upper intake manifold fasteners using a 12mm socket and 3/8" drive ratchet.
• Lift the upper intake manifold up and off. If it sticks, tap lightly by hand—do not pry on sealing surfaces.
• Immediately stuff clean shop rags into the exposed intake ports to prevent anything from falling in.
• Remove and discard the old upper intake gaskets.

Step 4: Replace the 3 rear-bank spark plugs (firewall-side)

• Unplug each rear ignition coil connector.
• Remove each coil bolt using a 10mm socket, then remove the coils.
• Vacuum out each plug well using a shop vacuum.
• Remove each spark plug using a 5/8" spark plug socket, 10" extension, and universal swivel joint.
• Install new plugs by hand first, then torque with a torque wrench: Torque to 25 Nm (18 ft-lbs).
• Apply a small dab of dielectric grease inside each coil boot, reinstall coils, and tighten coil bolts: Torque to 7 Nm (62 in-lbs).
• Reconnect all rear coil connectors.

Step 5: Reinstall the upper intake manifold

• Remove the rags from the intake ports (count them—make sure none remain).
• Install the new upper intake manifold gaskets.
• Set the upper intake manifold back in place, start all bolts by hand.
• Tighten the upper intake manifold fasteners evenly using a 12mm socket, then final torque with a torque wrench: Torque to 25 Nm (18 ft-lbs).
• Reconnect all vacuum/PCV hoses and electrical connectors you removed.

Step 6: Reinstall the intake duct and reconnect the battery

• Reinstall the intake duct and tighten clamps with a flathead screwdriver.
• Reinstall the engine cover using a 10mm socket.
• Reconnect the negative battery cable using a 10mm socket.

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✅ After Repair

• 🔍 Start the engine and listen for a smooth idle (no shaking/misfire).
• 🔎 Check for intake leaks: a loud hissing sound or high idle usually means a hose is off or a gasket is pinched.
• 🧪 If the check engine light comes on, re-check coil connectors first (most common).
• 🚗 Test drive 10 minutes, then re-check for any fuel/oil smells and re-confirm the intake duct clamps are tight.

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💰 DIY vs Shop Cost

Shop Cost: $450-$850 (parts + labor)

DIY Cost: $80-$180 (parts only)

You Save: $270-$770 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2.5-4.0 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.