🔧 Explorer - Spark Plug Replacement

On your Explorer’s 3.5L V6, you’ll replace all 6 spark plugs (and re-use the ignition coils unless they’re failing). The front bank is straightforward, but the rear bank sits under the upper intake manifold, so you’ll remove that to reach the back three plugs.

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 prevent thread damage in the cylinder heads.
• 🧯 Disconnect the negative battery cable to prevent accidental shorts and to protect electronics while unplugging sensors.
• 🧼 Keep dirt out of the intake: once the intake is off, cover the intake ports immediately.
• 👓 Use eye protection when blowing debris from spark plug wells.

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🔧 Required Tools

You'll need the following tools for this repair:

• 8mm socket
• 10mm socket
• 1/4" drive ratchet
• 3/8" drive ratchet
• 3/8" drive torque wrench (inch-lb capable)
• 3/8" drive torque wrench (ft-lb capable)
• 5/8" spark plug socket (rubber insert or магнит insert)
• 3/8" drive extension set (3", 6", 10")
• 3/8" drive swivel adapter
• Flat trim tool
• Needle-nose pliers
• Small pick tool
• Compressed air blow gun
• Shop vacuum
• Painter’s tape
• Fender cover
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (OE equivalent for 3.5L V6) - Qty: 6
• Upper intake manifold gasket set - Qty: 1
• Throttle body gasket - Qty: 1
• Dielectric grease - Qty: 1

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📋 Before You Begin

• 🅿️ Park on level ground, shift to Park, and set the parking brake.
• 🔌 Open the hood and use a 10mm socket to disconnect the negative battery terminal (move it aside so it can’t spring back).
• 🏷️ Use painter’s tape to label any vacuum hoses/electrical connectors you unplug (simple labels like “TB” for throttle body help a lot).

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover and open up access

• Pull up the engine cover to release it (use a flat trim tool if it’s stubborn).
• Remove the intake snorkel/air ducting as needed using an 8mm socket (and unplug any attached sensor connector using a small pick tool to lift the lock tab).

Step 2: Disconnect throttle body and intake connections

• Unplug the throttle body electrical connector (use a small pick tool to lift the locking tab gently).
• Disconnect the PCV/vacuum hoses from the upper intake using needle-nose pliers where spring clamps are used.
• Tip: Twist hoses first, then pull.

Step 3: Remove the throttle body (to clear intake removal)

• Remove the throttle body mounting bolts using a 8mm socket.
• Remove the throttle body and set it aside carefully (do not stress the wiring).
• Remove and discard the old throttle body gasket; you’ll install a new one later.
• During reassembly: Torque throttle body bolts to 10 Nm (89 in-lb)

Step 4: Remove the upper intake manifold (rear bank access)

• Remove the upper intake manifold bolts using a 10mm socket.
• Lift the upper intake manifold straight up and out.
• Immediately cover the lower intake ports with clean shop towels (use painter’s tape to hold towels in place).
• Remove and discard the old upper intake manifold gaskets.
• During reassembly: Torque upper intake manifold bolts to 10 Nm (89 in-lb)

Step 5: Remove ignition coils (one cylinder at a time)

• Pick one cylinder and stay with it start-to-finish to avoid mixing parts.
• Unplug the ignition coil connector (use a small pick tool to lift the lock, then pull).
• Remove the coil retaining bolt using a 8mm socket.
• Twist the coil boot slightly and pull the coil straight up.
• During reassembly: Torque ignition coil bolt to 8 Nm (71 in-lb)

Step 6: Clean the spark plug well and remove the old plug

• Blow out the spark plug well using a compressed air blow gun so dirt can’t fall into the cylinder.
• Remove the spark plug using a 5/8" spark plug socket, 3/8" drive extension, and a 3/8" drive ratchet.

Step 7: Install the new spark plug

• Start the new plug by hand using the 5/8" spark plug socket and an extension only (no ratchet at first) to avoid cross-threading.
• Tighten with a torque wrench: Torque spark plugs to 15 Nm (11 ft-lb)
• Apply a small amount of dielectric grease inside the coil boot before reinstalling the coil. (Dielectric grease is a non-conductive grease that helps prevent moisture and eases future removal.)

Step 8: Reinstall the ignition coil

• Push the coil straight down until you feel it fully seat on the spark plug.
• Install the coil bolt using an 8mm socket and then torque to 8 Nm (71 in-lb).
• Reconnect the coil electrical connector (make sure the lock tab clicks).

Step 9: Repeat for all 6 cylinders

• Repeat Steps 5–8 for each cylinder (rear bank is accessible now with the intake off).
• Use a 3/8" drive swivel adapter and different 3/8" drive extensions as needed for clearance.

Step 10: Reassemble intake and throttle body

• Remove all shop towels/tape from the intake ports.
• Install new upper intake manifold gaskets.
• Set the upper intake manifold in place and hand-start all bolts using a 10mm socket, then torque to 10 Nm (89 in-lb).
• Install the new throttle body gasket and reinstall the throttle body using an 8mm socket, then torque to 10 Nm (89 in-lb).
• Reconnect all vacuum/PCV hoses and electrical connectors.
• Reinstall the intake ducting using an 8mm socket and reinstall the engine cover.

Step 11: Reconnect the battery

• Reconnect the negative battery terminal using a 10mm socket.

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✅ After Repair

• 🔍 Double-check: all coil connectors clicked in, all hoses reattached, no tools left near the belts/fans.
• 🚗 Start the engine and let it idle for 2–3 minutes. A slightly rough idle for a few seconds can happen while the throttle and fuel trims re-learn.
• 🧪 Test drive 10–15 minutes and confirm no misfire, no check engine light, and normal acceleration.
• 🧾 If you had a check-engine light before, clear codes with a scan tool after confirming the repair.

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💰 DIY vs Shop Cost

Shop Cost: $450-$900 (parts + labor)

DIY Cost: $70-$180 (parts only)

You Save: $280-$830 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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