🔧 Ignition Coils - Replacement

On your Sierra, the ignition coils sit on top of the valve covers and each one feeds one spark plug. Replacing a bad coil is straightforward, but it’s important to disconnect the battery and keep dirt out of the plug wells.

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

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⚠️ Safety & Precautions

• Disconnect the negative battery cable before touching the ignition system.
• Do not pull on the coil wire/connector by the wire itself; use the connector body.
• Work on a cool engine. Hot valve covers and spark plugs can burn you.
• Keep dirt and water out of the spark plug wells.
• If a coil failed from an oil leak or coolant leak, fix the leak first or the new coil may fail again.

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🔧 Required Tools

You'll need the following tools for this repair:

• 8mm socket
• 3/8-inch ratchet
• 3-inch extension
• Torque wrench
• Trim clip tool
• Dielectric grease
• Safety glasses
• Nitrile gloves

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 8 if replacing all coils, or replace the failed coil only
• Ignition coil electrical connector lock - Qty: 1 if damaged
• 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 before starting.
• If the engine cover or intake duct blocks access, remove it first.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Disconnect battery power

• Use an 8mm socket to loosen and remove the negative battery cable.
• Move the cable aside so it cannot spring back and touch the post.

Step 2: Remove any parts blocking access

• If equipped, use a trim clip tool to remove the engine cover or intake duct fasteners.
• Lift the cover or duct out of the way to expose the coils on the valve covers.

Step 3: Unplug the ignition coil

• Press the connector release tab and pull the connector straight off the coil.
• Do not yank the wires.

Step 4: Remove the ignition coil

• Use an 8mm socket and 3/8-inch ratchet to remove the coil hold-down bolt.
• Twist the coil gently and pull it straight up out of the spark plug well.

Step 5: Inspect the spark plug well and boot

• Check for oil, water, or debris in the well.
• If the boot is torn, replace the coil. If the well has oil, repair the valve cover leak before installing the new coil.

Step 6: Install the new ignition coil

• Apply a thin film of dielectric grease inside the coil boot.
• Set the coil straight into the spark plug well.
• Install the hold-down bolt by hand first, then tighten with an 8mm socket.
• Torque to 10 Nm (89 in-lbs).

Step 7: Reconnect the coil connector

• Push the connector on until it clicks into place.
• Make sure the lock tab is fully seated.

Step 8: Repeat for the remaining coils

• Replace one coil at a time if you are only changing the failed unit.
• If replacing all coils, repeat the same steps for each cylinder.

Step 9: Reinstall removed components

• Reinstall any intake duct or engine cover removed earlier.
• Make sure all clamps and clips are fully seated.

Step 10: Reconnect the battery

• Reinstall the negative battery cable with an 8mm socket.
• Tighten it snugly. Do not overtighten.

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✅ After Repair

• Start the engine and listen for a smooth idle.
• Check the engine light. If it stays on, scan for misfire codes.
• Take a short test drive and confirm the misfire is gone.
• If the engine still misfires, the spark plugs, wiring, or fuel system may also need attention.

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💰 DIY vs Shop Cost

Shop Cost: $500-$1,200 (parts + labor)

DIY Cost: $160-$560 (parts only)

You Save: $340-$640 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1-2 hours.

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🎯 Ready to get started?

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