🔧 Highlander - Spark Plug Replacement

Your Highlander’s 2.7L 1AR-FE engine uses four long-life iridium spark plugs, one beneath each ignition coil. Replace them with the engine completely cold to protect the aluminum cylinder-head threads.

Difficulty Level: Beginner | Estimated Time: 1-1.5 hours

---

⚠️ Safety & Precautions

• ⚠️ Let the engine cool for at least three hours; removing plugs from a hot aluminum cylinder head can damage its threads.
• 🧤 Wear gloves and safety glasses because dirt may blow from the spark-plug wells.
• 🔌 The battery does not need to be disconnected, but keep the ignition switched off and the key away from your Highlander.
• 🚫 Do not apply anti-seize to the new plated spark-plug threads; it can cause over-tightening.
• 🧹 Clean each plug well before removing its plug so debris cannot enter the cylinder.

---

🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 14mm thin-wall spark-plug socket with rubber retainer
• 3/8-inch-drive ratchet
• 3/8-inch-drive 6-inch extension
• 3/8-inch-drive torque wrench rated 10-80 Nm
• Compressed-air blow gun with regulated air supply
• 0.040-inch wire spark-plug gap gauge
• Small flat-blade screwdriver
• Clean microfiber cloth
• Nitrile mechanic gloves
• Safety glasses

---

🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs equivalent to Toyota-specified Denso SC20HR11 - Qty: 4
• Dielectric ignition grease - Qty: 1 small tube

---

📋 Before You Begin

• 🅿️ Park your Highlander on level ground, select Park, apply the parking brake, and switch the ignition off.
• ❄️ Make sure the engine is completely cold before loosening any spark plug.
• 🧼 Clean loose dirt from the top of the engine before opening the spark-plug wells.
• 📏 The specified new-plug gap is 1.0-1.1 mm (0.039-0.043 inch). Iridium electrodes are fragile, so inspect the gap gently and do not pry against the center electrode.

---

🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine appearance cover

• Use the 10mm socket, extension, and ratchet to remove the cover fasteners.
• Lift the cover straight upward and place it aside.
• Use the clean microfiber cloth to wipe dirt from around the four ignition coils.

Step 2: Disconnect the first ignition coil

• Work on only one cylinder at a time so the connectors and coils cannot be mixed up.
• Press the electrical connector release and pull the connector straight off the coil.
• If the release is stubborn, use the small flat-blade screwdriver to press it gently. Do not pry on the wires.
• Push inward before pressing the release tab.

Step 3: Remove the ignition coil

• Use the 10mm socket, extension, and ratchet to remove the coil hold-down bolt.
• Twist the coil slightly by hand, then pull it straight upward.
• An ignition coil is the component that supplies high voltage to the spark plug.
• Inspect the rubber boot for oil, cracking, or burn marks. Oil inside the well indicates a sealing problem that should be repaired before installing plugs.

Step 4: Clean the spark-plug well

• Put on safety glasses.
• Use the compressed-air blow gun to remove dirt from the empty spark-plug well.
• Keep your face away from the well while blowing it clean.
• Do not remove the spark plug until no loose debris remains around it.

Step 5: Remove the old spark plug

• Fit the 14mm thin-wall spark-plug socket and 6-inch extension over the plug.
• Use the 3/8-inch-drive ratchet to turn the plug counterclockwise until it is completely loose.
• Lift the plug out with the socket’s rubber retainer.
• If the plug binds after initially loosening, stop and turn it slightly inward before continuing. Never force it.

Step 6: Inspect and prepare the new spark plug

• Compare the new and old plugs. Their thread length, seat shape, and terminal arrangement must match.
• Use the 0.040-inch wire spark-plug gap gauge to verify 1.0-1.1 mm (0.039-0.043 inch).
• Replace any new plug with a damaged electrode or incorrect gap. Do not bend the fine iridium center electrode.
• Keep the plug threads clean and dry. Do not use anti-seize.

Step 7: Hand-thread the new spark plug

• Place the new plug into the 14mm spark-plug socket attached only to the 6-inch extension.
• Lower it carefully into the well without dropping it.
• Turn the extension clockwise by hand for several full turns. It should rotate smoothly with little resistance.
• If it does not turn smoothly, remove it and start again to prevent cross-threading.
• Cross-threading means the plug enters the cylinder-head threads at the wrong angle.

Step 8: Torque the new spark plug

• Attach the 3/8-inch-drive torque wrench to the extension and spark-plug socket.
• Tighten the plug to 18 Nm (13 ft-lbs).
• Stop as soon as the torque wrench clicks. Do not tighten it again.

Step 9: Reinstall the ignition coil

• Apply a very small amount of dielectric ignition grease inside the opening at the end of the rubber coil boot. Keep grease away from the plug terminal and threads.
• Push the coil straight down until it seats fully over the spark plug.
• Install the hold-down bolt with the 10mm socket and extension.
• Use the torque wrench with the 10mm socket and tighten the coil bolt to 10 Nm (89 in-lbs).
• Reconnect the electrical connector until its lock clicks.

Step 10: Replace the remaining three spark plugs

• Repeat Steps 2 through 9 for the remaining coils and plugs, one cylinder at a time.
• Use compressed air before removing every plug.
• Torque every spark plug to 18 Nm (13 ft-lbs) and every coil bolt to 10 Nm (89 in-lbs).

Step 11: Reinstall the engine appearance cover

• Check that all four coil connectors are fully locked and no tools remain in the engine compartment.
• Position the appearance cover over its mounting points.
• Install its fasteners with the 10mm socket and ratchet until seated. Do not overtighten the plastic cover.

---

✅ After Repair

• ✅ Start the engine and let it idle for two to three minutes. It should run smoothly without shaking or misfiring.
• 👂 Listen for snapping or ticking near the ignition coils, which may indicate a loose coil or spark plug.
• 🚨 Confirm that the check-engine light remains off. If it flashes, shut the engine off immediately and recheck every coil connector.
• 🛣️ Take a short road test, then verify that the engine still idles smoothly.
• 📝 Record the mileage and replacement date. Toyota’s normal replacement interval for these iridium plugs is approximately 120,000 miles (192,000 km).

---

💰 DIY vs Shop Cost

Shop Cost: ₹8,000-₹15,000 (parts + labor)

DIY Cost: ₹4,000-₹8,000 (parts only)

You Save: ₹4,000-₹7,000 by doing it yourself!

Panipat labor rates and imported plug pricing vary. This repair takes a shop approximately 1-1.5 hours.

---

🎯 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.