🔧 Explorer - Spark Plug Replacement

Your Explorer uses 6 spark plugs (one per cylinder). On the 3.5L V6, the front three are easy to reach, but the rear three require removing the upper intake manifold so you can access the back bank safely.

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

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⚠️ Safety & Precautions

• ⚠️ Work on a cold engine to avoid burns and thread damage in the cylinder heads.
• ⚠️ Disconnect the negative battery cable to prevent accidental shorts while unplugging coils and sensors.
• ⚠️ Keep dirt out of the intake—cover open ports immediately after the manifold comes off.
• ⚠️ Do not over-tighten spark plugs; aluminum threads strip easily.

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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 (5-30 ft-lbs range)
• 6" extension (3/8" drive)
• 12" extension (3/8" drive)
• 3/8" universal joint (swivel)
• 5/8" spark plug socket (rubber insert or магнит)
• Flathead screwdriver
• Pliers
• Pick tool
• Compressed air blow gun
• Feeler gauge (0.051"-0.057")
• Shop towels
• Flashlight
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (OEM-style, gapped to spec) - 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 let the engine cool fully.
• Use a 10mm socket to disconnect the negative battery cable and isolate it so it can’t spring back.
• Set up a clean area for bolts and connectors. Phone photos help reassembly.

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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 (lift up if it’s push-on; if bolted, use an 8mm socket).
• Loosen the intake tube clamps with a flathead screwdriver.
• Unplug the MAF sensor connector (on the intake tube) by pressing the tab and pulling straight off.
• Remove the intake tube/air snorkel assembly and set it aside.

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

• On the front cylinder bank, unplug each ignition coil connector (press the tab, pull off).
• Remove each coil retaining bolt with a 8mm socket.
• Twist the coil boot slightly and pull the coil straight up and out.
• Blow out the spark plug well using compressed air blow gun so debris can’t fall into the cylinder.
• Remove the spark plug using a 5/8" spark plug socket, 6" extension, and 3/8" drive ratchet.
• Check the new plug gap with a feeler gauge (0.051"-0.057"). Adjust only if the plug manufacturer allows it.
• Thread the new plug in by hand using the spark plug socket and extension (no ratchet at first).
• Tighten with a torque wrench: Torque to 15 Nm (11 ft-lbs).
• Apply a thin smear of dielectric grease inside the coil boot (dielectric grease is a non-conductive silicone grease that helps prevent moisture and boot sticking).
• Reinstall coil and bolt: Torque to 7 Nm (62 in-lbs).

Step 3: Remove the throttle body connections

• Unplug the throttle body electrical connector.
• Disconnect any small vacuum/PCV hoses attached near the throttle body using pliers as needed.
• Remove the throttle body mounting bolts using a 8mm socket.
• Remove the throttle body and old gasket, then cover the opening with a shop towel.

Step 4: Remove the upper intake manifold (to reach rear plugs)

• Unplug the intake manifold sensor connectors you can access (label them with tape if needed).
• Disconnect remaining vacuum/PCV lines from the upper intake using pliers and a pick tool (a pick tool is a small hooked tool used to gently lift stubborn hose ends).
• Remove the upper intake manifold bolts using a 10mm socket.
• Lift the upper intake manifold off carefully.
• Immediately stuff clean shop towels into the exposed intake ports to keep hardware/debris out.

Step 5: Replace the rear bank spark plugs

• Unplug the rear ignition coil connectors.
• Remove coil bolts with an 8mm socket, then remove coils.
• Blow out each plug well using the compressed air blow gun.
• Remove each rear spark plug using a 5/8" spark plug socket, 12" extension, and 3/8" universal joint (swivel) (a swivel lets the socket bend to reach tight angles).
• Gap check the new plugs with the feeler gauge (0.051"-0.057").
• Install plugs by hand first, then torque: Torque to 15 Nm (11 ft-lbs).
• Add a small amount of dielectric grease inside each coil boot, reinstall coils, and torque coil bolts: Torque to 7 Nm (62 in-lbs).

Step 6: Reinstall the upper intake manifold and throttle body

• Remove the shop towels from the intake ports.
• Install the new upper intake manifold gaskets.
• Set the upper intake manifold in place and start all bolts by hand.
• Tighten the upper intake manifold bolts evenly: Torque to 10 Nm (89 in-lbs).
• Install a new throttle body gasket, reinstall the throttle body, and tighten bolts: Torque to 10 Nm (89 in-lbs).
• Reconnect all vacuum/PCV hoses and all electrical connectors you unplugged.

Step 7: Reinstall the intake duct and reconnect the battery

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

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✅ After Repair

• Start the engine and let it idle for 2-3 minutes. It may run slightly rough for a few seconds as the throttle relearns.
• Listen for hissing (vacuum leak). If you hear one, recheck intake hoses and the manifold seating.
• If the check engine light comes on, recheck coil connectors and any intake sensors you unplugged.
• Road test for 10-15 minutes, then recheck for any loose clamps or oil/vacuum smells.

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💰 DIY vs Shop Cost

Shop Cost: $350-$700 (parts + labor)

DIY Cost: $70-$220 (parts only)

You Save: $280-$480 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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