🔧 Ignition Coils - Replacement

Replacing the ignition coils on your Highlander means removing the engine cover, unplugging each coil, unbolting it, and installing the new coils over the spark plugs. A weak or failed ignition coil can cause misfires, rough idle, poor fuel economy, hesitation, or a check engine light.

Difficulty Level: Beginner | Estimated Time: 30-60 minutes

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⚠️ Safety & Precautions

• ⚠️ Work only on a cool engine so you do not burn your hands on hot metal or plastic parts.
• ⚠️ Disconnecting the 12V battery negative terminal is recommended to prevent accidental electrical shorts while unplugging ignition coil connectors.
• ⚠️ Do not pull on wiring harnesses. Pull only on the connector body after releasing the lock tab.
• ⚠️ Keep dirt and debris away from the spark plug tubes. Anything that falls in can cause engine damage.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 3/8-inch drive ratchet
• 3-inch socket extension
• 10mm wrench
• Trim clip removal tool
• Torque wrench in inch-pounds
• Compressed air can
• Dielectric grease packet
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Ignition coil - Qty: 1-4
• Dielectric grease - Qty: 1 packet

Tip: Replace only the failed coil if diagnosing a misfire, or replace all four if the coils are original and mileage is high.

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📋 Before You Begin

• Park your Highlander on level ground, shift to Park, and set the parking brake.
• Open the hood and let the engine cool completely.
• Use a 10mm wrench to disconnect the negative battery terminal. Move the cable aside so it cannot touch the battery post.
• If replacing more than one coil, replace them one at a time so the connectors and coil positions do not get mixed up.
• A dielectric grease packet contains electrical-safe silicone grease that helps seal the coil boot against moisture.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the Engine Cover

• Put on safety glasses and nitrile gloves.
• If your Highlander has a plastic engine cover, lift it straight up by hand to release the rubber mounting grommets.
• If any small plastic clips or retainers are fitted, use a trim clip removal tool to gently lift them without breaking them.
• Set the cover aside in a safe place.
• Pull upward evenly.

Step 2: Locate the Ignition Coils

• The 2.7L inline-4 engine has four ignition coils mounted along the top of the engine, one coil per cylinder.
• Each coil sits directly above a spark plug and has one electrical connector plugged into it.
• Use a compressed air can to blow light dirt away from the top of each coil before removal.

Step 3: Disconnect the Coil Connector

• Choose one coil to replace first.
• Press the connector lock tab with your thumb.
• Pull the connector straight back by hand from the coil.
• If it feels stuck, gently wiggle the connector body while pressing the tab.
• Do not use the wires as a handle.

Step 4: Remove the Ignition Coil Bolt

• Use a 10mm socket, 3-inch socket extension, and 3/8-inch drive ratchet to remove the coil retaining bolt.
• Set the bolt aside where it cannot fall into the engine bay.
• A retaining bolt is the small bolt that holds the ignition coil in place.

Step 5: Remove the Old Ignition Coil

• Grip the ignition coil body by hand.
• Twist it gently left and right to loosen the rubber boot from the spark plug.
• Pull the coil straight upward out of the spark plug tube.
• Inspect the old coil boot for oil, cracking, carbon tracking, or swelling.
• Carbon tracking looks like a thin black lightning-shaped line and can cause misfires.

Step 6: Prepare the New Ignition Coil

• Compare the new ignition coil to the old one by hand before installing it.
• Apply a very small amount of dielectric grease inside the end of the rubber coil boot.
• Do not pack the boot full of grease. A thin film is enough.
• Too much grease can cause misfires.

Step 7: Install the New Ignition Coil

• Slide the new ignition coil straight down into the spark plug tube by hand.
• Press down until you feel the boot seat onto the spark plug.
• Make sure the coil mounting hole lines up with the bolt hole.

Step 8: Tighten the Ignition Coil Bolt

• Start the 10mm coil bolt by hand to avoid cross-threading.
• Use a 10mm socket, 3-inch socket extension, and torque wrench in inch-pounds to tighten the bolt.
• Torque to 10 Nm (89 in-lbs)
• Do not overtighten. The valve cover threads can be damaged.

Step 9: Reconnect the Electrical Connector

• Push the electrical connector straight onto the new ignition coil by hand.
• Listen or feel for a click from the lock tab.
• Gently tug the connector body to make sure it is locked in place.

Step 10: Repeat for Remaining Coils

• If replacing more coils, repeat Steps 3 through 9 for each coil.
• Use the 10mm socket, 3-inch extension, ratchet, and torque wrench for each retaining bolt.
• Work one coil at a time to avoid mixing anything up.

Step 11: Reinstall the Engine Cover

• Position the plastic engine cover over its mounting points by hand.
• Press down evenly until the rubber grommets seat fully.
• If clips were removed, reinstall them with the trim clip removal tool or by pressing them in by hand.

Step 12: Reconnect the Battery

• Use a 10mm wrench to reconnect the negative battery terminal.
• Tighten the terminal clamp until snug.
• Do not overtighten the battery clamp.

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✅ After Repair

• Start your Highlander and let it idle for 1-2 minutes.
• Listen for smooth idle and confirm the engine does not shake.
• If the check engine light was on before, it may need several drive cycles to turn off after the misfire is fixed.
• If you have a basic scan tool, clear stored misfire codes after confirming the repair.
• Test drive gently for 10-15 minutes and confirm there is no hesitation under light acceleration.
• If the misfire remains, the spark plug, injector, wiring, compression, or another coil may need diagnosis.

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💰 DIY vs Shop Cost

Shop Cost: $180-$650 depending on whether one coil or all four are replaced

DIY Cost: $45-$320 parts only

You Save: $100-$330 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.5-1.0 hour.

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🎯 Ready to get started?

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