🔧 Ignition Coils - Replacement

Your Sierra uses individual coil-on-plug ignition coils, one per cylinder. Replacing a bad coil restores spark strength and helps fix misfires, rough idle, and check-engine lights. If one coil failed from age, the others may be close behind.

Difficulty Level: Intermediate | Estimated Time: 1-2 hours

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⚠️ Safety & Precautions

• Turn the engine off and let it cool completely before starting.
• Disconnect the negative battery cable before touching ignition components.
• Do not pull on ignition coil wires or connectors by force.
• Keep dirt out of the spark plug wells while the coils are removed.
• If a coil failed after an oil leak, fix the leak first so the new coil is not damaged.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 1/4-inch ratchet
• 1/4-inch extension
• Flat trim tool
• Small pick tool
• Dielectric grease
• Torque wrench
• Safety glasses
• Gloves
• Battery terminal wrench

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 1 per failed cylinder
• Ignition coil boot - Qty: 1 per coil, if not included with coil
• Dielectric grease - Qty: 1 tube

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📋 Before You Begin

• Park on level ground and set the parking brake.
• Let the engine cool so the coil packs and valve covers are safe to touch.
• Disconnect the negative battery cable before unplugging coils.
• If the engine cover is installed, remove it before starting.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Disconnect battery power

• Use a 10mm socket or battery terminal wrench to disconnect the negative battery cable.
• Move the cable aside so it cannot spring back into contact.

Step 2: Remove the engine cover

• Lift the engine cover straight up by hand if it is a push-on style.
• If it feels stuck, use a flat trim tool gently at the base tabs.

Step 3: Locate the failed coil

• Find the ignition coil on top of the valve cover above the spark plug for the misfiring cylinder.
• Tip: Cylinder numbering matters.

Step 4: Unplug the ignition coil

• Use a small pick tool to release the connector lock if needed.
• Press the connector tab and pull the connector straight off the coil.
• Do not pull on the wires.

Step 5: Remove the coil retaining bolt

• Use a 10mm socket, 1/4-inch ratchet, and 1/4-inch extension to remove the coil bolt.
• Set the bolt aside where it will not get lost.
• Torque on installation: 10 Nm (89 in-lbs)

Step 6: Remove the ignition coil

• Twist the coil gently to break it free, then pull it straight up out of the spark plug well.
• If the boot sticks, work it up slowly so you do not tear it.

Step 7: Inspect the spark plug well and boot

• Look for oil, water, or debris in the plug tube.
• If you see oil, repair the leak before installing the new coil.
• Use a clean cloth to wipe away loose dirt only.

Step 8: Prepare and install the new coil

• Apply a small amount of dielectric grease inside the new boot.
• Set the coil straight over the spark plug and press it down fully.
• Install the coil bolt by hand first.
• Use the 10mm socket and torque wrench to tighten the bolt to 10 Nm (89 in-lbs).

Step 9: Reconnect the electrical connector

• Push the connector onto the coil until it clicks.
• Make sure the lock tab is fully seated.

Step 10: Reinstall the engine cover and battery cable

• Reinstall the engine cover by pressing it into place.
• Reconnect the negative battery cable with the 10mm socket or battery terminal wrench.

Step 11: Verify the repair

• Start the engine and listen for smooth idle.
• Check for a check-engine light and confirm the misfire is gone.
• If the light stays on, clear codes and road test the truck.

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✅ After Repair

• Let the engine idle for a few minutes and confirm it runs smoothly.
• Take a short road test and check for hesitation or flashing check-engine light.
• If a misfire code returns, the spark plug or fuel injector may also need diagnosis.

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💰 DIY vs Shop Cost

Shop Cost: $180-$480 (parts + labor)

DIY Cost: $40-$160 (parts only)

You Save: $140-$320 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.8-1.5 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.