🔧 Highlander - Ignition Coil Replacement

Your Highlander uses coil-on-plug ignition coils (one coil per cylinder). Replacing a bad coil fixes misfires, rough running, flashing check-engine lights, and poor power.

Difficulty Level: Intermediate | Estimated Time: 0.8-2.5 hours (front bank only vs all coils)

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⚠️ Safety & Precautions

• ⚠️ Work on a cool engine to avoid burns.
• ⚠️ Disconnect the negative battery terminal if you’ll remove the intake manifold or work near the throttle body wiring.
• ⚠️ Do not pull on wiring; release connectors by the lock tab first.
• ⚠️ Keep dirt out of the spark plug wells; debris can fall into the cylinder.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 12mm socket
• 1/4" drive ratchet
• 3/8" drive ratchet
• 3" socket extension
• 6" socket extension
• Torque wrench (inch-pound)
• Torque wrench (foot-pound)
• Flat trim removal tool
• Needle-nose pliers
• Small pick tool
• Shop vacuum
• Flashlight
• Nitrile gloves
• Safety glasses
• OBD2 scan tool (basic) (specialty)

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 1-6
• Dielectric grease - Qty: 1
• Upper intake manifold gasket set - Qty: 1 (only if manifold is removed)
• Throttle body gasket - Qty: 1 (only if throttle body is removed)

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📋 Before You Begin

• Park on level ground, shift to Park, and set the parking brake.
• Let the engine cool fully.
• If you’re doing rear-bank coils and need more room: disconnect the negative battery cable using a 10mm socket.
• Use a shop vacuum to clean around the coil areas before pulling anything apart.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Lift the plastic engine cover straight up to pop it off its rubber grommets (no tools usually needed).
• If yours has fasteners, remove them with a 10mm socket.

Step 2: Decide access path (front bank vs rear bank)

• Front bank coils (radiator side) are usually easy to reach—continue to Step 3.
• Rear bank coils (firewall side) may be tight. If you can’t comfortably reach the coil bolts/connectors, go to Step 6 for the “more room” method.

Step 3: Unplug the ignition coil electrical connector

• Press the connector lock tab and pull the connector straight off the coil.
• If it’s stubborn, use a small pick tool to gently lift the lock tab while pulling.
• Don’t pry on the wires.

Step 4: Remove the coil hold-down bolt

• Remove the coil bolt using a 10mm socket with a 3" socket extension and 1/4" drive ratchet.

Step 5: Remove and install the coil

• Twist the coil slightly, then pull it straight up out of the spark plug well.
• Put a tiny smear of dielectric grease inside the new coil boot. (Dielectric grease is a non-conductive grease that helps seal out moisture and makes future removal easier.)
• Push the new coil straight down until it fully seats on the spark plug.
• Reinstall the coil bolt with a 10mm socket, then Torque to 9 Nm (80 in-lbs) using a torque wrench (inch-pound).
• Reconnect the electrical connector until it clicks.

Step 6: Rear bank “more room” method (if needed)

• Remove the intake air duct/clamps using needle-nose pliers (for spring clamps) and a 10mm socket (for worm clamps, if equipped).
• Unclip/remove any plastic retainers using a flat trim removal tool.
• If access is still too tight, remove the upper intake manifold hardware using a 12mm socket and 3/8" drive ratchet, then lift it enough to access the rear coils.
• Keep track of hoses/connectors. Use a flashlight and move slowly.
• If the upper intake manifold is removed/loosened, replace the gaskets during reassembly.

Step 7: Reassemble intake parts (if removed)

• Reinstall the upper intake manifold and start all fasteners by hand first.
• Tighten evenly in a crisscross pattern with a 12mm socket, then Torque to 21 Nm (15 ft-lbs) using a torque wrench (foot-pound).
• Reinstall the intake duct and clamps using a 10mm socket and needle-nose pliers.
• If you disconnected the battery earlier, reconnect the negative cable using a 10mm socket.

Step 8: Reinstall engine cover

• Press the cover back onto the grommets, or tighten fasteners with a 10mm socket if equipped.

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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, use an OBD2 scan tool (basic) (specialty) to clear codes and confirm misfires don’t return.
• Take a short test drive and recheck for any loose intake clamps or hissing (vacuum leak sound).

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💰 DIY vs Shop Cost

Shop Cost: $250-$750 (parts + labor, depends on how many coils and rear-bank access)

DIY Cost: $40-$420 (parts only, depends on how many coils)

You Save: $210-$330+ by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.0-2.5 hours.

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🎯 Ready to get started?

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