🔧 Spark Plugs - Replacement

Your Sierra uses coil-on-plug ignition, so each spark plug sits under an individual ignition coil. The job is straightforward, but the rear cylinders can be tight on a Crew Cab, so take your time and keep the coils organized.

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

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⚠️ Safety & Precautions

• Let the engine cool completely before starting. Hot aluminum cylinder heads can be damaged by over-tightening.
• Disconnect the negative battery cable before removing ignition coils.
• Do not pull on the spark plug wire harness by force; release connectors carefully.
• Keep dirt out of the spark plug wells. Debris can fall into the cylinders.
• Use anti-seize only if the plug manufacturer specifically allows it. Many modern plugs are pre-coated.

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🔧 Required Tools

You'll need the following tools for this repair:

• 5/8" spark plug socket
• 3/8" ratchet
• 3/8" drive extension set
• 10mm socket
• Torque wrench
• Flat-blade trim tool
• Dielectric grease
• Compressed air
• Safety glasses
• Nitrile gloves

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs - Qty: 8
• Dielectric grease - Qty: 1
• Ignition coil boots - Qty: 8, if damaged

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📋 Before You Begin

• Park on level ground and set the parking brake.
• Turn the ignition off and remove the key/fob from the vehicle.
• Disconnect the negative battery cable with a 10mm socket.
• Work on one cylinder at a time to avoid mixing parts.
• Keep each coil with its original cylinder.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Disconnect battery power

• Use a 10mm socket to remove the negative battery cable.
• Move the cable aside so it cannot touch the battery post.

Step 2: Remove the engine cover and intake ducting if equipped

• Use a flat-blade trim tool if any clips need to be released.
• Set all fasteners aside in order.

Step 3: Remove the ignition coil from one cylinder

• Use a 10mm socket to remove the coil hold-down bolt.
• Pull the ignition coil straight up with a gentle twist.
• Inspect the coil boot for oil, tears, or carbon tracking.
• Work one cylinder at a time.

Step 4: Clean the spark plug well

• Use compressed air to blow dirt out of the plug tube before removing the plug.
• This helps keep debris out of the cylinder.

Step 5: Remove the old spark plug

• Use a 5/8" spark plug socket, 3/8" ratchet, and extension to remove the plug.
• Turn counterclockwise slowly so the threads come out cleanly.
• If a plug feels stuck, stop and work it back and forth carefully.

Step 6: Gap and install the new spark plug

• Check the new plug gap before installation. The plug should match the spec for your Sierra.
• Thread the new plug in by hand first using the spark plug socket and extension.
• Once seated, use a torque wrench to tighten to 18 Nm (13 ft-lbs).
• Hand-start every plug to avoid cross-threading.

Step 7: Reinstall the ignition coil

• Apply a small amount of dielectric grease inside the coil boot if desired.
• Push the coil straight down onto the new plug until fully seated.
• Install the coil bolt with a 10mm socket and tighten to 10 Nm (89 in-lbs).

Step 8: Repeat for the remaining cylinders

• Move to the next cylinder and repeat Steps 3 through 7.
• Keep the coils and bolts organized as you go.

Step 9: Reassemble and reconnect power

• Reinstall any intake ducting or engine cover removed earlier.
• 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 misfire or flashing check engine light.
• If the engine shakes or runs rough, recheck coil seating and plug connections.
• Test drive the truck and make sure acceleration feels normal.
• If the plugs were badly worn, a short relearn drive can help the PCM adjust fuel trims.

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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 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.