🔧 Maxima - Spark Plug Replacement

On your Maxima, the front 3 spark plugs are easy to access, but the rear 3 sit under the upper intake plenum (upper intake manifold). You’ll remove a few intake parts, swap all 6 plugs, then reassemble with new gaskets to prevent vacuum leaks.

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

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⚠️ Safety & Precautions

• ⚠️ Work on a fully cool engine to avoid burns and damaged threads in the aluminum cylinder heads.
• ⚠️ Disconnect the negative battery terminal before unplugging throttle body/intake sensors.
• ⚠️ Do not drop anything into the intake ports—stuff clean rags in openings when the plenum is off.
• ⚠️ Use only hand tools to start spark plugs—cross-threading is expensive.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• Floor jack (rated 3-ton minimum)
• Jack stands (rated 3-ton minimum)
• Wheel chocks
• 10mm socket
• 12mm socket
• 1/4" drive ratchet
• 3/8" drive ratchet
• 3/8" drive torque wrench (10-80 ft-lbs range)
• 6" 3/8" extension
• 12" 3/8" extension
• 3/8" universal joint
• 14mm thin-wall spark plug socket (3/8" drive)
• Flathead screwdriver
• Needle-nose pliers
• Trim clip remover
• Pick tool
• Compressed air blow gun
• Clean shop rags
• Paint marker

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs (OEM-spec) - Qty: 6
• Upper intake plenum gasket set - Qty: 1
• Throttle body gasket - Qty: 1
• Dielectric grease - Qty: 1

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📋 Before You Begin

• Park on level ground, set the parking brake, and chock the rear wheels.
• Open the hood and let the engine cool completely.
• Use a 10mm socket to disconnect the negative battery terminal and isolate it so it can’t spring back.
• Use a paint marker to mark/vaguely label any similar vacuum hoses so they go back to the same spot.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover and intake duct

• Pull the engine cover upward to release it (it’s held by grommets).
• Loosen the air intake hose clamps using a flathead screwdriver.
• Unplug the intake sensor(s) by pressing the lock tab, then remove the intake ducting.

Step 2: Replace the front bank spark plugs (easier side)

• Unplug one ignition coil connector at a time (press the tab, pull straight off).
• Remove the coil bolt with a 10mm socket, then pull the coil straight up.
• Blow out the spark plug well using compressed air blow gun so dirt can’t fall into the cylinder.
• Remove the spark plug using a 14mm thin-wall spark plug socket with a 6" 3/8" extension and 3/8" drive ratchet.
• Install the new plug by hand using the spark plug socket and extension only (no ratchet at first). Hand-threading prevents cross-threading.
• Tighten the plug with a 3/8" drive torque wrench: Torque to 25 Nm (18 ft-lbs).
• Apply a small amount of dielectric grease inside the coil boot, reinstall the coil, then tighten the coil bolt: Torque to 9 Nm (80 in-lbs).
• Repeat for the other 2 front plugs (do one cylinder at a time to avoid mix-ups).

Step 3: Remove components to access the rear bank plugs

• Disconnect any vacuum hoses from the upper intake area using needle-nose pliers (move spring clamps back first).
• Unplug the throttle body connector and any upper intake connectors (press tab, pull straight).
• Remove the throttle body fasteners with a 10mm socket and set the throttle body aside carefully.
• Remove the upper intake plenum bolts/nuts using a 12mm socket.
• Lift the upper intake plenum off. Immediately stuff clean shop rags into the exposed intake openings.
• Use a pick tool to remove old gaskets without gouging surfaces.

Step 4: Replace the rear bank spark plugs

• Unplug and remove each rear ignition coil using a 10mm socket (same as the front bank).
• Blow out each spark plug well with the compressed air blow gun.
• Remove each rear spark plug using the 14mm thin-wall spark plug socket, 12" 3/8" extension, and 3/8" universal joint as needed.
• Install new plugs by hand first, then torque each plug with a 3/8" drive torque wrench: Torque to 25 Nm (18 ft-lbs).
• Reinstall coils and torque coil bolts: Torque to 9 Nm (80 in-lbs).

Step 5: Reinstall the upper intake plenum and throttle body

• Install new upper intake plenum gaskets (make sure they sit fully in their grooves).
• Set the upper intake plenum in place and hand-start all bolts/nuts.
• Tighten upper intake plenum bolts/nuts evenly using a 12mm socket: Torque to 25 Nm (18 ft-lbs).
• Install a new throttle body gasket, then reinstall the throttle body using a 10mm socket: Torque to 10 Nm (89 in-lbs).
• Reconnect all hoses and electrical connectors until they click.

Step 6: Reinstall intake ducting and reconnect the battery

• Reinstall the intake duct and tighten clamps using a flathead screwdriver.
• Reinstall the engine cover by pressing it into the grommets.
• Reconnect the negative battery terminal using a 10mm socket.

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✅ After Repair

• Start the engine and let it idle for 2–3 minutes. It may idle rough briefly while the throttle/ECM relearns.
• Check for a hissing sound (vacuum leak) around the upper intake and throttle body area.
• If you get a check engine light or high/unstable idle, re-check all intake hoses/connectors and gasket seating.
• If idle stays abnormal after a short drive, you may need an idle relearn procedure (scan tool capable of Nissan idle learn is best).

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💰 DIY vs Shop Cost

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

DIY Cost: $120-$260 (parts only)

You Save: $330-$590 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?

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