🔧 Yukon - Spark Plug Replacement

On your Yukon, the spark plugs fire the air/fuel mixture in each cylinder. Replacing worn plugs helps prevent misfires, rough idle, and reduced fuel economy, and it keeps the ignition system from working too hard.

Difficulty Level: Intermediate | Estimated Time: 1.5-3.0 hours

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⚠️ Safety & Precautions

• 🔥 Work on a fully cool engine to avoid burns and thread damage.
• 🔌 Disconnect the negative battery cable to prevent accidental coil firing.
• 🧯 Keep dirt out of the plug holes; debris can damage the engine.
• 🧤 Use eye protection when blowing out plug wells with air.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• 3/8" drive ratchet
• 3/8" drive torque wrench (10-30 ft-lbs range)
• 5/8" spark plug socket
• 3/8" drive extension set (3", 6", 10")
• 3/8" drive universal joint
• 10mm socket
• Trim removal tool
• Small flathead screwdriver
• Compressed air blow gun
• Flashlight
• Dielectric grease
• Spark plug gap gauge (wire style)

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (OEM-equivalent iridium) - Qty: 8
• Coil-to-plug wires (optional, if cracked or loose) - Qty: 8

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📋 Before You Begin

• Park on level ground, shift to Park, and set the parking brake.
• Let the engine cool completely (at least 1 hour).
• Open the hood and disconnect the negative battery cable using a 10mm socket.
• Do one cylinder at a time to avoid mix-ups.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover (if equipped)

• Grip the cover and pull upward to release it from the mounting grommets.
• If any fasteners are present, remove them with a 10mm socket.

Step 2: Unplug one ignition coil connector

• Choose one cylinder to start with.
• Press the connector lock and unplug the coil electrical connector using a small flathead screwdriver only if needed.
• Don’t pull on the wires—pull on the connector body.

Step 3: Remove the coil mounting bolt and move the coil aside

• Remove the coil mounting bolt with a 10mm socket.
• Lift the coil off its bracket and position it out of the way without stressing the wiring.

Step 4: Remove the coil-to-plug wire (plug lead)

• Twist the boot a little to break it free, then pull it straight off the spark plug.
• Coil-to-plug wire (definition): the short insulated lead that connects the coil to the spark plug.
• If the boot is stubborn, use a trim removal tool gently under the boot lip.

Step 5: Clean the spark plug well

• Blow compressed air down around the plug using a compressed air blow gun and safety glasses.
• This prevents dirt from falling into the cylinder when the plug is removed.

Step 6: Remove the spark plug

• Use a 5/8" spark plug socket, 3/8" drive extension, and 3/8" drive ratchet to loosen and remove the plug.
• If access is tight, add a 3/8" drive universal joint.
• Lift the plug out carefully with the socket.

Step 7: Check and prepare the new spark plug

• Check the gap with a spark plug gap gauge (wire style).
• Install only plugs that match OEM spec for your Yukon; most OEM-equivalent plugs come pre-gapped, but always verify.
• Do not apply anti-seize unless the plug manufacturer specifically requires it (most modern plugs are plated).

Step 8: Install and torque the new spark plug

• Thread the new plug in by hand using the 5/8" spark plug socket and an extension (no ratchet at first) to avoid cross-threading.
• Torque the spark plug with a 3/8" drive torque wrench: Torque to 15 Nm (11 ft-lbs).
• If it won’t thread by hand, stop and realign.

Step 9: Reinstall the plug wire and coil

• Apply a small amount of dielectric grease inside the plug boot.
• Push the boot onto the plug until you feel it seat/click.
• Reinstall the coil and tighten the coil bolt with a 10mm socket: Torque to 10 Nm (89 in-lbs).
• Reconnect the electrical connector until it clicks.

Step 10: Repeat for all remaining cylinders

• Repeat Steps 2–9 for each cylinder, working one at a time.
• Use a flashlight to confirm every connector is fully seated.

Step 11: Reinstall engine cover and reconnect battery

• Reinstall the engine cover by pressing it back into the grommets.
• Reconnect the negative battery cable using a 10mm socket.

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✅ After Repair

• Start the engine and listen for a smooth idle (no shaking or flashing check engine light).
• Test drive 5–10 minutes and recheck for any warning lights.
• If you had a misfire light before, scan and clear codes after verifying the repair.
• Recheck that every coil connector is clicked in and no tools are left in the engine bay.

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💰 DIY vs Shop Cost

Shop Cost: $350-$650 (parts + labor)

DIY Cost: $80-$180 (parts only)

You Save: $270-$470 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.5-2.5 hours.

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🎯 Ready to get started?

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