🔧 Expedition - Spark Plug Replacement

Replacing the spark plugs on your Expedition helps restore smooth idle, strong acceleration, fuel economy, and proper ignition performance. The 3.5L EcoBoost uses coil-on-plug ignition, so each ignition coil sits directly on top of a spark plug.

Difficulty Level: Intermediate | Estimated Time: 2-3 hours

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⚠️ Safety & Precautions

• ⚠️ Work only on a completely cool engine. Aluminum cylinder heads can be damaged if plugs are removed hot.
• ⚠️ Disconnect the negative battery cable before unplugging ignition coils.
• ⚠️ Do not allow dirt, bolts, or tools to fall into the spark plug wells.
• ⚠️ Do not over-tighten spark plugs. The cylinder heads are aluminum.
• ⚠️ Replace one spark plug at a time so parts do not get mixed up.

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🔧 Required Tools

You'll need the following tools for this repair:

• 8mm socket
• 10mm socket
• 7mm socket
• 5/8-inch spark plug socket
• 3/8-inch drive ratchet
• 3/8-inch drive 6-inch extension
• 3/8-inch drive 3-inch extension
• 3/8-inch drive universal joint
• Torque wrench, inch-pound range
• Torque wrench, foot-pound range
• Spark plug gap gauge
• Compressed air blow gun
• Trim clip removal tool
• Needle-nose pliers
• Pick tool set
• Dielectric grease
• Anti-seize compound
• Magnetic pickup tool
• Fender cover
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs, pre-gapped for 3.5L EcoBoost - Qty: 6
• Ignition coil boots - Qty: 6
• Intake tube clamp or damaged hose clamp - Qty: As needed

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📋 Before You Begin

• Park your Expedition on level ground, shift to Park, and set the parking brake.
• Let the engine cool fully. Overnight cooling is best for a first-time DIYer.
• Open the hood and install a fender cover to protect the paint.
• Use a 10mm socket to loosen the negative battery terminal, then move the cable aside so it cannot touch the battery post.
• A spark plug socket is a deep socket with a rubber insert or magnet that holds the plug so it does not fall.
• A universal joint is a small flexible adapter that helps your socket reach angled spark plugs.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the Engine Cover

• Lift the plastic engine cover upward by hand to release it from the rubber mounting grommets.
• Set the cover aside in a safe place.
• Pull straight up, not sideways.

Step 2: Remove Intake Tubing for Access

• Use a 7mm socket to loosen the clamps on the air intake tube.
• Use a pick tool to gently release any small hose retainers attached to the intake tube.
• Use needle-nose pliers to release spring clamps if equipped.
• Remove the intake tube and set it aside.
• Cover any open intake opening with a clean rag so nothing falls inside.

Step 3: Identify the Ignition Coils

• Locate the six ignition coils on top of the engine, three on each side.
• Each coil has one electrical connector and one small retaining bolt.
• Work on only one coil and spark plug at a time.

Step 4: Unplug One Ignition Coil

• Use your finger or a pick tool to gently lift the connector lock tab.
• Pull the connector straight back from the ignition coil.
• Do not pull on the wires.
• Press the tab, then pull.

Step 5: Remove the Ignition Coil

• Use an 8mm socket and ratchet to remove the ignition coil retaining bolt.
• Twist the ignition coil gently by hand, then pull it straight upward.
• Inspect the coil boot for oil, cracking, carbon tracking, or swelling.
• Replace the coil boot if it is damaged or brittle.

Step 6: Clean the Spark Plug Well

• Put on safety glasses.
• Use a compressed air blow gun to blow dirt out of the spark plug well.
• Keep your face away from the area while blowing out debris.
• This step prevents dirt from falling into the engine when the plug is removed.

Step 7: Remove the Old Spark Plug

• Use a 5/8-inch spark plug socket, 3/8-inch drive 6-inch extension, and ratchet to loosen the spark plug.
• For tight rear plugs, use a 3/8-inch drive universal joint and 3-inch extension as needed.
• Turn counterclockwise slowly until the plug is fully loose.
• Lift the spark plug out with the spark plug socket.
• If the plug feels stuck, stop and tighten it slightly, then loosen again slowly.

Step 8: Check the New Spark Plug Gap

• Use a spark plug gap gauge to verify the new plug gap.
• The correct gap for the 3.5L EcoBoost is typically 0.028 inch.
• Do not pry against the fine iridium center electrode.
• Use only plugs specified for the 3.5L EcoBoost.

Step 9: Install the New Spark Plug by Hand

• Place the new spark plug into the 5/8-inch spark plug socket.
• Use the 6-inch extension by hand, without the ratchet, to start threading the plug.
• Turn clockwise gently until the plug is finger-tight.
• If it does not turn smoothly, remove it and start again.
• Hand-starting prevents thread damage.

Step 10: Torque the Spark Plug

• Attach a torque wrench to the 5/8-inch spark plug socket and extension.
• Tighten the spark plug to Torque to 15 Nm (11 ft-lbs).
• Do not add extra tightening after the torque wrench clicks.
• Use anti-seize only if the spark plug manufacturer specifically allows it. Many modern iridium plugs have coated threads and do not need it.

Step 11: Reinstall the Ignition Coil

• Apply a small amount of dielectric grease inside the end of the coil boot.
• Push the ignition coil straight down onto the spark plug until seated.
• Install the coil bolt by hand first.
• Use an 8mm socket and inch-pound torque wrench to tighten the coil bolt to Torque to 8 Nm (71 in-lbs).

Step 12: Reconnect the Ignition Coil Connector

• Push the electrical connector onto the ignition coil until it clicks.
• Gently tug the connector to make sure it is locked.

Step 13: Repeat for the Remaining Five Spark Plugs

• Repeat Steps 4 through 12 for each remaining spark plug.
• Use the 3/8-inch drive universal joint for the rear plugs where access is tighter.
• Keep bolts and coils organized as you work.
• Replace all six spark plugs as a set.

Step 14: Reinstall Intake Tubing

• Remove the clean rag from the intake opening.
• Reinstall the intake tube by hand, making sure it is fully seated.
• Use a 7mm socket to tighten the intake tube clamps snugly.
• Reconnect any hoses or retainers removed earlier.

Step 15: Reinstall the Engine Cover and Battery Cable

• Push the engine cover straight down onto its rubber grommets by hand.
• Reconnect the negative battery cable.
• Use a 10mm socket to tighten the negative battery terminal snugly.
• Do not overtighten the battery terminal.

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✅ After Repair

• Start your Expedition and let it idle for 2-3 minutes.
• Listen for smooth idle and check that there are no ticking, hissing, or misfire sounds.
• If the engine runs rough, shut it off and recheck each ignition coil connector.
• Test drive gently for 10-15 minutes.
• If the check engine light was on before the repair, use a scan tool to clear codes after confirming the engine runs smoothly.
• After the test drive, recheck that the intake tube clamps are secure.

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💰 DIY vs Shop Cost

Shop Cost: $450-$750 (parts + labor)

DIY Cost: $90-$180 (parts only)

You Save: $270-$660 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2-3 hours.

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🎯 Ready to get started?

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