🔧 TLX - Spark Plug Replacement

Replacing the spark plugs restores strong ignition, smooth idle, and good fuel economy. On your TLX, the plugs sit under the ignition coils on top of the engine, so this is a straightforward top-of-engine job.

Difficulty Level: Beginner | Estimated Time: 1.0-2.0 hours

Assumption: stock 2.4L with coil-on-plug ignition.

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⚠️ Safety & Precautions

• ⚠️ Work on a cold engine to avoid burns and damaged threads.
• ⚠️ Disconnect the negative battery cable to prevent accidental shorts.
• ⚠️ Keep dirt out of the spark plug holes; debris can damage the engine.
• ⚠️ Start spark plugs by hand first to avoid cross-threading.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 3/8" drive ratchet
• 3/8" drive extension (6")
• 14mm thin-wall spark plug socket (magnetic or rubber insert)
• Torque wrench (3/8" drive, 10-30 Nm range)
• Flat trim tool
• Needle-nose pliers
• Compressed air blow gun
• Shop vacuum
• Dielectric grease
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs (OEM-equivalent) - Qty: 4
• Ignition coil boots (optional, if torn/oil-soaked) - Qty: 4

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📋 Before You Begin

• Park on level ground and let the engine cool fully.
• Open the hood and remove any loose items around the engine.
• Use a 10mm socket to disconnect the battery negative cable and tuck it aside so it can’t spring back.
• Set your new plugs nearby and keep them clean; iridium tips are delicate.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Pull up on the engine cover to release the rubber grommets, or use a flat trim tool to help gently pry if it’s tight.
• Set the cover aside where it won’t get stepped on.

Step 2: Unplug and unbolt the ignition coils

• Each cylinder has an ignition coil (a “coil-on-plug” unit that sits directly on the spark plug).
• Press the connector tab and pull the connector off each coil; use needle-nose pliers carefully only if needed.
• Remove the coil hold-down bolt using a 10mm socket and 3/8" ratchet.
• Lift the coil straight up and out. Wiggle gently; don’t yank.
• Torque on reassembly: Torque to 12 Nm (9 ft-lbs)

Step 3: Clean the spark plug wells

• Use a shop vacuum around each plug hole first.
• Blow out the plug wells with a compressed air blow gun so dirt can’t fall into the cylinder when the plug comes out.
• Wear safety glasses—dust will fly.

Step 4: Remove the old spark plugs

• Insert a 14mm thin-wall spark plug socket with a 3/8" extension (6") and 3/8" ratchet into the plug hole.
• Turn counterclockwise to loosen and remove the plug.
• Pull the plug out with the socket. If it feels stuck, stop and work it slowly to avoid thread damage.

Step 5: Install the new spark plugs (by hand first)

• Confirm the new plugs match the old ones in length and seat type.
• Do not bend the electrode; iridium plugs are typically pre-gapped. Don’t “regap” iridium plugs.
• Place a new plug into the 14mm spark plug socket and lower it into the hole.
• Thread it in by hand using only the extension (6") (no ratchet yet) until it seats smoothly.
• Tighten with a torque wrench: Torque to 18 Nm (13 ft-lbs)
• Avoid anti-seize; it can change torque.

Step 6: Reinstall the ignition coils

• Put a small dab of dielectric grease inside each coil boot (this helps prevent moisture and makes future removal easier).
• Push each coil straight down until fully seated on the plug.
• Install the hold-down bolts using a 10mm socket and snug them.
• Final tighten with a torque wrench: Torque to 12 Nm (9 ft-lbs)
• Reconnect each coil electrical connector until it clicks.

Step 7: Reinstall the engine cover and reconnect the battery

• Reinstall the engine cover by lining it up and pressing down firmly onto the grommets.
• Reconnect the negative battery cable using a 10mm socket and tighten securely.

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✅ After Repair

• Start the engine and let it idle for 1-2 minutes; it should run smooth with no shaking.
• Listen for ticking/air leaks around the coil area (there shouldn’t be any).
• If the check engine light comes on or it runs rough, shut it off and re-check that every coil connector is fully clicked in.

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💰 DIY vs Shop Cost

Shop Cost: $250-$450 (parts + labor)

DIY Cost: $50-$120 (parts only)

You Save: $200-$330 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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