🔧 Pathfinder - Spark Plug Replacement

On your Pathfinder’s 3.5L V6, changing spark plugs means removing the upper intake plenum to reach the rear bank of plugs. New plugs help prevent misfires, rough idle, poor fuel economy, and hard starts.

Difficulty Level: Advanced | Estimated Time: 2.5-4.5 hours

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⚠️ Safety & Precautions

• ⚠️ Work on a fully cool engine to avoid burns and damaged threads.
• ⚠️ Disconnect the negative battery cable to prevent accidental short circuits.
• ⚠️ Keep dirt out of the intake—cover open ports with clean shop towels.
• ⚠️ Do not over-tighten spark plugs; aluminum heads strip easily.
• ⚠️ Avoid pulling on wires—disconnect electrical connectors by the tabs.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• 10mm socket
• 12mm socket
• 14mm socket
• 3/8" drive ratchet
• 3/8" drive torque wrench (10-40 ft-lbs range)
• 3/8" drive extension set (3", 6", 10")
• Universal joint adapter (3/8" drive)
• 5/8" spark plug socket (rubber insert)
• Phillips screwdriver
• Flat trim clip tool
• Needle-nose pliers
• Small pick tool
• Compressed air blow gun
• Shop vacuum
• Permanent marker
• Magnetic pickup tool
• Flashlight
• Clean shop towels

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (OEM-style iridium, pre-gapped) - Qty: 6
• Upper intake plenum gasket set - Qty: 1
• Throttle body gasket - Qty: 1
• Dielectric grease - Qty: 1
• Intake hose clamps (assorted) - Qty: 1

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📋 Before You Begin

• Park on level ground, shift to Park, and set the parking brake.
• Let the engine cool completely (at least 1-2 hours).
• Use a 10mm socket to disconnect the negative battery cable and isolate it so it can’t spring back.
• Label any vacuum hoses/connectors with a permanent marker so they go back to the same place.
• Take photos before unplugging anything.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover and air intake duct

• Remove the engine cover by releasing its fasteners using a 10mm socket (if equipped) and lifting it off.
• Loosen the intake tube clamps using a Phillips screwdriver and remove the intake duct.
• Unclip any plastic retainers using a flat trim clip tool.

Step 2: Disconnect the throttle body and hoses

• Unplug the throttle body electrical connector using a small pick tool to lift the lock tab, then pull the connector straight off.
• Remove any small vacuum hoses from the intake tube/plenum using needle-nose pliers to slide clamps back.
• Move hoses aside so you have clear access to the upper intake plenum.
• Don’t pry on the throttle body housing.

Step 3: Remove the upper intake plenum

• Disconnect remaining vacuum lines and electrical connectors attached to the plenum using a small pick tool and your hands.
• Remove the plenum mounting bolts using a 12mm socket with a 3/8" drive ratchet and extensions.
• Lift the plenum straight up and off. If it sticks, gently work it loose by hand (do not use metal pry tools).
• Immediately stuff clean ports with clean shop towels so nothing falls into the engine.

Step 4: Remove ignition coils (one cylinder at a time)

• Pick one coil, unplug its connector by releasing the tab using a small pick tool.
• Remove the coil bolt using a 10mm socket.
• Twist the coil boot slightly, then pull the coil straight up and out.
• Do one coil and plug at a time.

Step 5: Clean around the spark plug wells

• Blow out debris from the spark plug well using a compressed air blow gun.
• Use a shop vacuum to remove loosened dirt.
• This prevents grit from falling into the cylinder when the plug comes out.

Step 6: Remove the old spark plugs

• Use a 5/8" spark plug socket, 3/8" drive ratchet, and the needed extensions to loosen and remove the plug.
• If access is tight, use a universal joint adapter (3/8" drive).
• Lift the plug out carefully; use a magnetic pickup tool if needed.

Step 7: Install the new spark plugs

• Check each new plug matches the old one in length and seat style.
• Start each plug by hand using the 5/8" spark plug socket and an extension only (no ratchet) so it threads in smoothly.
• Tighten using a 3/8" drive torque wrench: Torque to 25 Nm (18 ft-lbs).
• Apply a small dab of dielectric grease inside the coil boot (dielectric grease is an electrical-safe grease that helps prevent moisture and sticking).

Step 8: Reinstall ignition coils

• Push the coil straight down until it fully seats on the new plug.
• Install the coil bolt using a 10mm socket, then finish with a torque wrench: Torque to 9 Nm (80 in-lbs).
• Reconnect the coil electrical connector until it clicks.

Step 9: Reinstall the upper intake plenum with new gaskets

• Remove the old gaskets and install the new upper plenum gaskets by hand.
• Remove the shop towels from the intake ports and double-check nothing fell in using a flashlight.
• Set the plenum in place carefully and hand-start all bolts.
• Tighten bolts evenly using a 12mm socket in a crisscross pattern.
• Final tighten using a torque wrench: Torque to 25 Nm (18 ft-lbs).

Step 10: Reinstall the intake duct and reconnect everything

• Reconnect all vacuum hoses and electrical connectors you removed.
• Reinstall the intake duct and tighten clamps using a Phillips screwdriver.
• Reinstall the engine cover using a 10mm socket if applicable.
• Reconnect the negative battery cable using a 10mm socket.

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✅ After Repair

• Start the engine and let it idle for 2-3 minutes. It may idle slightly rough for a few seconds while it relearns airflow.
• Listen for vacuum leaks (a loud hissing sound). If you hear hissing, shut it off and recheck plenum gaskets and hoses.
• Make sure there’s no check engine light. If there is, recheck coil connectors and any unplugged sensors.
• Do a short test drive and confirm smooth acceleration with no hesitation.

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💰 DIY vs Shop Cost

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

DIY Cost: $90-$220 (parts only)

You Save: $360-$630 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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