🔧 Spark Plugs - Replacement

Your Sierra uses coil-on-plug ignition, so each plug is accessed by removing the ignition coil on top of the engine. The job is straightforward, but the rear plugs are tighter to reach, so take your time and keep dirt out of the plug holes.

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

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⚠️ Safety & Precautions

• Work only on a cold engine. Hot aluminum threads can strip easily.
• Disconnect the negative battery cable before starting.
• Keep tools and loose parts away from the intake openings and plug holes.
• Do not overtighten the new plugs. The cylinder head is aluminum.
• If a plug is hard to remove, work it slowly to avoid thread damage.

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🔧 Required Tools

You'll need the following tools for this repair:

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

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs - Qty: 8
• Dielectric grease - Qty: 1

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📋 Before You Begin

• Park on level ground and set the parking brake.
• Let the engine cool completely.
• Disconnect the negative battery cable using a 10mm socket.
• Use compressed air to blow dirt away from each coil and plug well before removal.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover, if equipped

• Lift the cover straight up by hand. Some trucks use rubber grommets that pop off.

Step 2: Remove the ignition coils

• Use an 8mm socket to remove the coil hold-down bolt on each cylinder.
• Pull the coil straight up and off the spark plug.
• Unplug the electrical connector by pressing the lock tab first.
• Keep each coil with its original cylinder.

Step 3: Clean around each spark plug

• Use compressed air to blow out the plug wells.
• This keeps dirt from falling into the cylinder when the plug comes out.

Step 4: Remove the old spark plugs

• Use a 5/8-inch spark plug socket, ratchet, and extension to loosen each plug.
• If needed, add the universal joint adapter for tighter rear plugs.
• Turn each plug counterclockwise until it comes out.
• If a plug feels stuck, work it back and forth gently. Do not force it.

Step 5: Prep the new spark plugs

• Check that each new plug is correct for your engine and properly gapped if needed.
• Apply a tiny amount of anti-seize compound only if the plug manufacturer allows it.
• Add a small dab of dielectric grease inside each coil boot.
• Less is better with grease.

Step 6: Install the new spark plugs

• Thread each plug in by hand first using the spark plug socket and extension.
• This prevents cross-threading.
• Once seated, tighten each plug with a torque wrench to 20 Nm (15 ft-lbs).

Step 7: Reinstall the ignition coils

• Push each coil fully onto its spark plug.
• Reconnect each electrical connector until it clicks.
• Install the coil bolt with an 8mm socket and tighten to 10 Nm (89 in-lbs).

Step 8: Reinstall the engine cover and battery cable

• Press the engine cover back into place, if equipped.
• Reconnect the negative battery cable with a 10mm socket.

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✅ After Repair

• Start the engine and listen for smooth idle.
• Check for misfires, rough running, or a flashing check engine light.
• If the engine runs rough, recheck coil connectors and plug seating.
• Take a short test drive and confirm normal acceleration.

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💰 DIY vs Shop Cost

Shop Cost: $250-$450 (parts + labor)

DIY Cost: $50-$120 (parts only)

You Save: $200-$330 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2-4 hours.

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🎯 Ready to get started?

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