🔧 Spark Plugs - Replacement

Your Sierra’s spark plugs sit under the ignition coils on top of the engine. This job is straightforward, but you need to work carefully so you don’t crack a coil boot or cross-thread a plug in the aluminum cylinder head.

Difficulty Level: Intermediate | Estimated Time: 1.5-2.5 hours

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⚠️ Safety & Precautions

• Let the engine cool fully before starting. Hot aluminum threads can be damaged easily.
• Disconnect the negative battery cable before removing ignition coils. The negative cable is the black battery cable.
• Do not pull on ignition wires. This engine uses individual ignition coils at each plug.
• Keep dirt out of the spark plug wells. Debris can fall into the cylinder head if you remove a plug with the area dirty.
• Use compressed air carefully and wear eye protection.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 8mm socket
• 3/8-inch ratchet
• 3-inch extension
• 6-inch extension
• Spark plug socket 14mm with rubber insert
• Torque wrench
• Feeler gauge
• Flat blade trim tool
• Dielectric grease
• Compressed air
• Safety glasses
• Mechanic gloves

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs - Qty: 4
• Dielectric grease - Qty: 1

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📋 Before You Begin

• Park on level ground and set the parking brake.
• Make sure the engine is completely cool.
• Open the hood and remove loose items from the engine bay.
• Disconnect the negative battery cable with a 10mm socket.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover and air inlet parts

• Use a 10mm socket or 8mm socket to remove any engine cover fasteners, if equipped.
• Lift off the cover by hand.
• If the intake tube blocks access, use a flat blade trim tool to release clamps or clips and move the intake duct aside.

Step 2: Disconnect and remove the ignition coils

• Use a flat blade trim tool or your fingers to release each coil electrical connector lock.
• Unplug each coil connector carefully.
• Use a 10mm socket with a ratchet and short extension to remove the coil hold-down bolts.
• Lift each ignition coil straight up by hand. Twist gently if it sticks.

Step 3: Clean the spark plug wells

• Use compressed air to blow dirt away from each plug well.
• Wear safety glasses while doing this.
• Make sure no grit falls into the cylinder head.

Step 4: Remove the old spark plugs

• Use a spark plug socket 14mm with rubber insert, 6-inch extension, and ratchet to remove each spark plug.
• Turn counterclockwise slowly.
• If a plug feels tight, stop and work it back and forth gently. Do not force it.

Step 5: Check and prepare the new plugs

• Use a feeler gauge to verify the gap on each new plug.
• Set the gap to 0.030 in if adjustment is needed.
• Apply a very small amount of dielectric grease inside each coil boot.

Step 6: Install the new spark plugs

• Start each plug by hand using the spark plug socket 14mm with rubber insert and extension.
• Thread them in slowly by hand first to avoid cross-threading.
• Once seated, tighten with a torque wrench to 23 Nm (17 ft-lbs).

Step 7: Reinstall the ignition coils

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

Step 8: Reassemble the intake and engine cover

• Reinstall any intake tube or air inlet parts with the flat blade trim tool if needed.
• Reinstall the engine cover by hand and tighten fasteners with the correct socket.
• Reconnect the negative battery cable with a 10mm socket.

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✅ After Repair

• Start the engine and let it idle.
• Listen for misfires, rough idle, or ticking noises.
• Check the engine light. If it flashes, shut the engine off and recheck your work.
• Test drive gently and confirm smooth acceleration.

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💰 DIY vs Shop Cost

Shop Cost: $220-$420 (parts + labor)

DIY Cost: $45-$120 (parts only)

You Save: $175-$300 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.