🔧 Explorer - Spark Plug Replacement

On your Explorer’s 3.5L V6, the front bank of spark plugs is easy to reach, but the rear bank sits under the upper intake manifold (the “top half” of the intake). This job is very doable at home if you work cleanly and stay organized, because you’ll be removing parts to access the rear plugs.

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

Assumption: Stock 3.5L NA V6 with coil-on-plug ignition and upper intake removal required for rear plugs.

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⚠️ Safety & Precautions

• ⚠️ Work on a fully cool engine to avoid burns and stripped threads.
• ⚠️ Disconnect the negative battery cable to prevent accidental shorts.
• ⚠️ Keep dirt out of the intake ports; cover openings with clean rags immediately.
• ⚠️ Do not over-tighten spark plugs; the cylinder heads are aluminum.
• ⚠️ Avoid anti-seize on Ford plated spark plugs unless the plug maker specifies it.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• 10mm socket
• 8mm socket
• 7mm socket
• 5/8" spark plug socket
• 3/8" drive ratchet
• 3/8" drive extension set (3", 6", 12")
• 3/8" drive swivel joint
• Torque wrench (3/8" drive, 5-30 ft-lbs range)
• Torque wrench (inch-pound, 40-200 in-lbs range)
• Flathead screwdriver
• Trim clip tool
• Compressed air blow gun
• Feeler gauge set
• Magnetic pickup tool
• Masking tape and marker
• Clean shop rags

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (OEM-style, correct heat range) - 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 and open the hood.
• Let the engine cool completely (at least 1-2 hours after driving).
• Use 10mm socket to disconnect the negative battery terminal and tuck it aside.
• Use masking tape and marker to label any hoses/connectors you remove. This prevents mix-ups during reassembly.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover and air inlet

• Pull up to remove the engine cover (it’s held by grommets).
• Use a flathead screwdriver to loosen the air intake hose clamp(s).
• Use a trim clip tool if needed to release any push-clips holding the intake snorkel, then remove the air inlet ducting for working room.

Step 2: Unplug and remove the ignition coils (front bank)

• On the front bank (closest to the radiator), unplug each coil electrical connector by releasing the lock tab.
• Use an 8mm socket to remove each coil hold-down bolt.
• Twist the coil slightly, then pull it straight up to remove it.
• A coil is the “spark maker” that sits on top.

Step 3: Remove the front bank spark plugs

• Use compressed air blow gun to blow dirt out of each spark plug well (the tube the plug sits down in).
• Use a 5/8" spark plug socket, 3/8" ratchet, and the needed extension to remove each spark plug.
• Check the new plug gap with a feeler gauge set and adjust only if the plug maker allows it. Typical spec is about 0.051-0.057 in (always follow the plug box label if it differs).
• Start the new plug by hand using the spark plug socket and extension only (no ratchet at first) to avoid cross-threading.
• Tighten using a torque wrench: Torque to 15 Nm (11 ft-lbs).

Step 4: Prep for upper intake manifold removal (to access rear plugs)

• Locate the upper intake manifold (the large plastic intake on top of the engine).
• Use masking tape and marker to label vacuum hoses and electrical connectors you’ll remove.
• Disconnect the electrical connectors you can reach on the intake (such as MAP sensor and throttle body area) by releasing their lock tabs.
• Remove the PCV/vacuum hoses from the intake by gently twisting and pulling. Use a flathead screwdriver only if needed to help, and don’t tear the hose.

Step 5: Remove the throttle body from the intake

• Unplug the throttle body connector.
• Use a 7mm socket to loosen the intake boot clamp at the throttle body (if still attached), then move the boot aside.
• Use a 8mm socket to remove the throttle body bolts.
• Remove the throttle body and set it aside carefully.
• Plan to install a new throttle body gasket during reassembly.

Step 6: Remove the upper intake manifold

• Double-check that all connectors and hoses attached to the upper intake are disconnected.
• Use a 10mm socket to remove the upper intake manifold bolts.
• Lift the upper intake manifold straight up and off.
• Immediately place clean shop rags into the exposed intake ports to prevent dropping anything into the engine.
• Dropping a bolt in an intake port is bad.

Step 7: Replace the rear bank spark plugs

• Unplug the rear bank ignition coils and remove their hold-down bolts using an 8mm socket.
• Remove the coils (twist and pull up).
• Blow out spark plug wells using the compressed air blow gun.
• Use a 5/8" spark plug socket, extension set, and a swivel joint to remove rear spark plugs.
• Hand-thread the new plugs first, then torque with a torque wrench: Torque to 15 Nm (11 ft-lbs).

Step 8: Reinstall coils

• Apply a tiny amount of dielectric grease inside each coil boot. (This helps prevent moisture and makes future removal easier.)
• Install coils onto the plugs and push down until fully seated.
• Install coil bolts using an 8mm socket, then snug them evenly.

Step 9: Reinstall the upper intake manifold (with new gaskets)

• Remove the shop rags from the intake ports.
• Remove old upper intake gaskets and install the new upper intake manifold gasket set.
• Set the upper intake manifold back into place carefully.
• Install the intake bolts finger-tight first using a 10mm socket, then tighten evenly in a crisscross pattern.
• Final tighten using an inch-pound torque wrench: Torque to 10 Nm (89 in-lbs).

Step 10: Reinstall throttle body and intake ducting

• Install the throttle body with a new throttle body gasket.
• Tighten throttle body bolts with an inch-pound torque wrench: Torque to 10 Nm (89 in-lbs).
• Reconnect the throttle body electrical connector.
• Reinstall the air intake duct and tighten clamp(s) using a flathead screwdriver or 7mm socket (depending on clamp type).
• Reconnect all hoses/connectors you labeled.
• Reinstall the engine cover (press down into the grommets).

Step 11: Reconnect the battery

• Use a 10mm socket to reconnect the negative battery terminal and tighten it snug.

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✅ After Repair

• Turn the key to ON (engine off) for 10 seconds, then OFF. Repeat once. This helps the throttle system “wake up” after being unplugged.
• Start the engine and let it idle for 2-3 minutes. Expect a slightly rough idle for a few seconds while it relearns.
• Listen for vacuum leaks (hissing). If you hear one, recheck intake hose clamps and vacuum hoses.
• Road test for 10-15 minutes. Make sure there’s no check engine light and acceleration feels smooth.

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💰 DIY vs Shop Cost

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

DIY Cost: $60-$180 (parts only)

You Save: $270-$790 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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