🔧 Spark Plugs - Replacement

Your Sierra’s spark plugs fire the air-fuel mix in each cylinder. On the 4.3L V6, they sit under the ignition coils on top of the engine, so the job is straightforward but tight in places.

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

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⚠️ Safety & Precautions

• Work on a cold engine. Hot aluminum heads can damage threads and burn you.
• Disconnect the negative battery cable before removing coils. A dead battery helps prevent accidental sparks.
• Do not drop dirt into the spark plug wells. Keep the area clean before removing plugs.
• Use a torque wrench. Over-tightening can strip the cylinder head.
• If you have to move wiring or hoses, do it gently. The coil connectors and boots can get brittle.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 5/8-inch spark plug socket
• 3/8-inch ratchet
• 3-inch extension
• 6-inch extension
• Torque wrench
• Gap gauge
• Trim panel tool
• Dielectric grease
• Compressed air
• 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 gasket set - Qty: 0 if not disturbed
• Dielectric grease - Qty: 1

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📋 Before You Begin

• Park on level ground and set the parking brake.
• Let the engine cool fully.
• Open the hood and remove any engine cover if equipped.
• Disconnect the negative battery cable before touching ignition coils.
• Label coil locations if you want to keep everything in the same order.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Use your hands to lift off the engine cover if equipped.
• Set it aside in a safe spot.

Step 2: Disconnect the battery

• Use a 10mm socket to remove the negative battery cable.
• Move the cable away from the battery so it cannot touch the terminal.

Step 3: Remove the ignition coils

• Use a 10mm socket and 3/8-inch ratchet with an extension to remove each coil bolt.
• Unplug the coil electrical connector by pressing the tab and pulling straight back.
• Twist each coil gently, then lift it out.
• Do not yank on the wire.

Step 4: Clean the spark plug wells

• Use compressed air to blow dirt out of each plug well.
• This keeps debris from falling into the cylinder.

Step 5: Remove the old spark plugs

• Use a 5/8-inch spark plug socket, 3-inch extension, and ratchet to loosen each plug.
• Turn counterclockwise until each plug comes free.
• Lift the plugs out carefully.

Step 6: Check and set the plug gap

• Use a gap gauge to check each new plug before installation.
• Set them to the specification listed on the plug box or service data.
• Pre-gapped does not always mean correct.

Step 7: Install the new spark plugs

• Thread each plug in by hand first using the 5/8-inch spark plug socket and extension.
• This prevents cross-threading, which can damage the cylinder head.
• Once seated by hand, use a torque wrench to tighten each plug to 18 Nm (13 ft-lbs).

Step 8: Reinstall the ignition coils

• Apply a small amount of dielectric grease inside each coil boot.
• Slide each coil straight down onto its plug.
• Reinstall the coil bolts using a 10mm socket and tighten to 10 Nm (89 in-lbs).
• Reconnect each coil connector until it clicks.

Step 9: Reconnect the battery and reassemble

• Reinstall the negative battery cable using a 10mm socket.
• Reinstall the engine cover if equipped.

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✅ After Repair

• Start the engine and let it idle.
• Listen for rough running, misfires, or ticking noises.
• Check that the check engine light stays off.
• If the truck shakes or runs rough, recheck coil connectors and plug torque.
• After a short test drive, make sure the engine runs smoothly under light throttle.

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💰 DIY vs Shop Cost

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

DIY Cost: $40-$120 (parts only)

You Save: $210-$380 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?

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.