🔧 Spark Plugs - Replacement

Your F-150 uses six spark plugs, one per cylinder. On the 3.5L EcoBoost, access is tight, so work carefully and keep dirt out of the plug wells. Replacing all six plugs together helps restore smooth running, fuel economy, and cold-start performance.

Difficulty Level: Intermediate | Estimated Time: 2-4 hours

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⚠️ Safety & Precautions

• Let the engine cool completely before starting. Hot aluminum cylinder heads can be damaged if plugs are removed hot.
• Disconnect the negative battery cable before removing coils. This reduces the chance of accidental misfires or electrical damage.
• Use compressed air or a vacuum to clean around each plug before removal. Dirt falling into the cylinder can cause engine damage.
• Do not overtighten the new plugs. The cylinder heads are aluminum and the threads can strip easily.
• Use only the correct plugs specified for the 3.5L EcoBoost. Wrong plugs can cause misfires and turbo-related drivability issues.

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🔧 Required Tools

You'll need the following tools for this repair:

• 3/8-inch ratchet
• 8mm socket
• 10mm socket
• 5/8-inch spark plug socket
• 6-inch extension
• Torque wrench
• Flat-blade trim tool
• Compressed air nozzle
• Dielectric grease
• Anti-seize compound
• Feeler gauge
• Gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs - Qty: 6
• Valve cover/coil boot seals - Qty: 6
• Dielectric grease - Qty: 1 tube

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📋 Before You Begin

• Park on level ground and set the parking brake.
• Let the engine cool fully.
• Disconnect the negative battery cable using a 10mm socket.
• Have the new plugs ready and compare the gap to the service spec before installation.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove engine cover and intake ducting

• Use a flat-blade trim tool to release the engine cover clips, if equipped.
• Use an 8mm socket to loosen the intake duct clamps and remove any tubes blocking access to the coils.
• Set the parts aside in order so reassembly is easier.

Step 2: Disconnect the ignition coils

• Use your fingers or a small pick to release each coil connector tab.
• Remove the coil hold-down bolts with a 10mm socket.
• Pull each ignition coil straight up. If it sticks, twist gently while lifting.
• Keep coils in cylinder order.

Step 3: Clean the spark plug wells

• Use compressed air nozzle to blow debris out of each plug well.
• If dirt is packed in, vacuum the area first, then blow it clean.
• This keeps debris from dropping into the cylinder.

Step 4: Remove the old spark plugs

• Use a 5/8-inch spark plug socket, 6-inch extension, and 3/8-inch ratchet to loosen each plug.
• Turn counterclockwise slowly. If a plug feels tight, work it back and forth gently.
• Remove one plug at a time so you do not mix up cylinders.

Step 5: Inspect and prepare the new plugs

• Check each new plug gap with a feeler gauge.
• Install only plugs that match the correct gap spec for your engine.
• Apply a tiny amount of anti-seize compound only if required by the plug manufacturer; many coated plugs do not need it.
• Apply a small dab of dielectric grease inside each coil boot.

Step 6: Install the new spark plugs

• Thread each plug in by hand first using the 5/8-inch spark plug socket and extension.
• If a plug does not thread easily, stop and restart to avoid cross-threading.
• Tighten each plug with a torque wrench to 13 Nm (115 in-lbs).
• Hand-start every plug first.

Step 7: Reinstall the ignition coils

• Push each coil firmly onto its spark plug until it seats fully.
• Reinstall the coil bolts with a 10mm socket.
• Tighten the coil bolts to 8 Nm (71 in-lbs).
• Reconnect each electrical connector until it clicks.

Step 8: Reassemble the intake and engine cover

• Reinstall any intake tubes and tighten the clamps with an 8mm socket.
• Reinstall the engine cover, if equipped.
• Reconnect the negative battery cable with a 10mm socket.

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✅ After Repair

• Start the engine and let it idle.
• Listen for smooth idle and check for warning lights.
• If the engine runs rough, recheck coil connectors and plug seating.
• Take a short test drive and confirm normal acceleration.
• If a misfire light returns, scan for codes before driving further.

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💰 DIY vs Shop Cost

Shop Cost: $250-$500 (parts + labor)

DIY Cost: $60-$140 (parts only)

You Save: $190-$360 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?

HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.