🔧 Terrain - Ignition Coil Replacement

Your Terrain uses coil-on-plug ignition coils (one coil per cylinder). Replacing a bad coil can fix misfires, rough idle, and a flashing check engine light, and it’s a straightforward job with basic hand tools.

Difficulty Level: Beginner | Estimated Time: 0.5-1.5 hours

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⚠️ Safety & Precautions

• ⚠️ Let the engine cool fully before starting; coils sit on a hot valve cover.
• ⚠️ Turn the ignition OFF and keep the key/fob away from the vehicle while unplugging coils.
• ⚠️ Disconnect the negative battery cable to prevent accidental electrical damage.
• ⚠️ Do not pull on wiring; pull on the connector body.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 1/4" drive ratchet
• 3" extension
• Torque wrench (inch-pound, 20–200 in-lb range)
• Small flathead screwdriver
• Trim removal tool
• Needle-nose pliers
• Shop light
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 1 (or Qty: 4 if replacing all)
• Dielectric grease - Qty: 1
• Ignition coil boot - Qty: 1 (optional, if torn/oil-soaked)

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📋 Before You Begin

• Park on level ground, shift to Park, and set the parking brake.
• Let the engine cool completely.
• Open the hood and disconnect the negative battery cable using a 10mm socket. Tuck it aside so it can’t spring back.
• Dielectric grease helps prevent moisture in the boot.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover (if equipped)

• Grip the cover at the corners and pull upward evenly; if it resists, use a trim removal tool to gently lift at the grommets.
• Set the cover aside where it won’t get stepped on.

Step 2: Locate the ignition coils

• The coils are lined up on top of the engine (one per cylinder), each with an electrical connector.
• Use a shop light so you can clearly see the connector locks.

Step 3: Unplug the coil electrical connector

• Release the connector lock using a small flathead screwdriver (a lock tab is a small plastic “safety” that prevents accidental unplugging).
• Press the release and pull the connector straight back by hand—do not pull on the wires.

Step 4: Remove the coil hold-down bolt

• Remove the coil bolt using a 10mm socket, 3" extension, and 1/4" drive ratchet.
• Set the bolt aside where it won’t fall into the engine bay.

Step 5: Remove the ignition coil

• Twist the coil slightly left/right, then pull straight up to remove it from the spark plug well.
• If it’s stuck, keep twisting while pulling—don’t pry hard against plastic parts.

Step 6: Inspect for oil or water in the spark plug well

• Look down the hole with a shop light.
• If you see engine oil pooled in the well, stop and address the leak first (commonly a valve cover gasket issue), or the new coil may fail early.

Step 7: Install the new coil

• Put a small dab of dielectric grease inside the end of the coil boot (the rubber tube) using a gloved finger.
• Push the coil straight down until it fully seats on the spark plug.
• Install the hold-down bolt by hand first to avoid cross-threading.
• Tighten the bolt using a torque wrench (inch-pound): Torque to 89 in-lb (10 Nm).

Step 8: Reconnect the electrical connector

• Push the connector on until it clicks.
• Re-engage the connector lock (if equipped) using a small flathead screwdriver.

Step 9: Reinstall the engine cover

• Align the cover with the mounting grommets and press down firmly by hand until it seats.

Step 10: Reconnect the battery

• Reconnect the negative battery cable using a 10mm socket.
• Snug it securely (do not overtighten and strip the clamp).

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✅ After Repair

• Start the engine and let it idle for 1–2 minutes. It should run smooth with no shaking.
• If the check engine light was on, it may take a few drive cycles to turn off; a basic scan tool can clear codes immediately.
• Test drive for 10–15 minutes and re-check for warning lights or a misfire feel.
• If it still misfires, the next common causes are spark plugs, a vacuum/boost leak, or fuel injector issues.

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💰 DIY vs Shop Cost

Shop Cost: $250-$650 (parts + labor)

DIY Cost: $60-$320 (parts only)

You Save: $190-$330 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.6-1.2 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.