🔧 Terrain - Spark Plug Replacement

Replacing the spark plugs helps your engine start easier, idle smoother, and maintain fuel economy. On your Terrain’s 2.4L, the plugs sit under the ignition coils on top of the engine, so this is a straightforward job with basic hand tools.

Difficulty Level: Beginner | Estimated Time: 1.0-1.5 hours

Assumption: stock 2.4L coil-on-plug ignition (no modifications).

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⚠️ Safety & Precautions

• ⚠️ Work on a cool engine (hot aluminum threads can strip).
• ⚠️ Keep dirt out of the spark plug holes (debris can damage the engine).
• ⚠️ Do not over-tighten spark plugs (cross-threading is expensive to fix).
• ⚠️ Battery disconnect is not required, but keep the key off and don’t crank the engine with coils unplugged.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• 10mm socket
• 3/8" drive ratchet
• 3/8" drive extension set
• 5/8" spark plug socket
• Torque wrench (3/8" drive, inch-pound/foot-pound capable)
• Small flat trim tool
• Compressed air blow gun
• Feeler gauge (0.040" blade)
• Dielectric grease
• Flashlight

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (iridium, OE-equivalent) - Qty: 4

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📋 Before You Begin

• Park on level ground, shift to Park, and set the parking brake.
• Let the engine fully cool (at least 30-60 minutes).
• Open the hood and have your flashlight ready so you can clearly see each coil and plug well.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover (if equipped)

• Grip the cover and pull upward firmly to pop it off its rubber grommets. Use a small flat trim tool only if needed to gently help lift an edge.
• Set the cover aside where it won’t get stepped on.

Step 2: Unplug the ignition coil connectors

• Use a small flat trim tool to help release the connector lock if it’s tight.
• Pull the connector straight off each coil (don’t yank the wires).
• Tip: Do one coil at a time.

Step 3: Remove the ignition coils

• Use a 10mm socket with a 3/8" drive ratchet to remove the coil hold-down bolt.
• Twist the coil slightly, then pull it straight up to remove it from the spark plug tube.
• Repeat for all four coils (or keep going one-by-one).
• Torque to 10 Nm (89 in-lbs) when reinstalling coil bolts.
• Coil = the plug “boot” assembly on top.

Step 4: Clean around each spark plug well

• Blow out dirt from the spark plug tube using a compressed air blow gun.
• This prevents grit from falling into the cylinder when the plug comes out.

Step 5: Remove the old spark plug

• Install a 5/8" spark plug socket on a 3/8" drive extension and 3/8" drive ratchet.
• Turn counterclockwise to loosen, then spin it out by hand with the ratchet once it’s loose.
• Lift the plug out with the socket.

Step 6: Check and prepare the new spark plug

• Use a feeler gauge (0.040" blade) to verify the gap is about 0.040" (1.0 mm) (most iridium plugs come pre-gapped).
• Do not force-bend the tiny center electrode on iridium plugs; if the gap is way off, replace the plug.
• Apply a small smear of dielectric grease inside the coil boot (dielectric grease is a non-conductive grease that helps prevent moisture and makes future removal easier).
• Skip anti-seize unless plug maker requires it.

Step 7: Install the new spark plug (by hand first)

• Place the new plug in the 5/8" spark plug socket with the 3/8" drive extension.
• Lower it into the hole and thread it in by hand using the extension only (no ratchet at first).
• If it doesn’t screw in smoothly, back it out and try again—this prevents cross-threading.

Step 8: Torque the spark plug

• Use a torque wrench (3/8" drive, inch-pound/foot-pound capable) with the 5/8" spark plug socket to tighten the plug.
• Torque to 25 Nm (18 ft-lbs).

Step 9: Reinstall the ignition coil

• Push the coil straight down until it fully seats on the spark plug.
• Install the coil bolt using a 10mm socket and 3/8" drive ratchet.
• Finish with a torque wrench: Torque to 10 Nm (89 in-lbs).

Step 10: Reconnect coil connectors and reinstall the engine cover

• Push each connector on until it clicks/locks in place.
• Reinstall the engine cover by lining up the grommets and pressing down firmly.
• Use a flashlight to do a final look for any unplugged connectors.

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✅ After Repair

• Start the engine and let it idle for 30-60 seconds. It should run smooth with no flashing check-engine light.
• If it runs rough: shut it off and re-check that every coil connector is fully seated and each coil is bolted down.
• Test drive 5-10 minutes and confirm no hesitation under light acceleration.

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💰 DIY vs Shop Cost

Shop Cost: $180-$320 (parts + labor)

DIY Cost: $40-$90 (parts only)

You Save: $140-$230 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.0-1.5 hours.

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🎯 Ready to get started?

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