🔧 Highlander - Ignition Coil Replacement

Replacing the ignition coils on your Highlander is a straightforward repair. The ignition coils sit on top of the engine and send high voltage to the spark plugs so the engine can fire correctly.

This job is usually done when there is a misfire, rough idle, flashing check engine light, or stored misfire codes. On the 2.7L inline-4, the coils are accessible from the top of the engine.

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

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⚠️ Safety & Precautions

• ⚠️ Work only with the engine cool to avoid burns.
• ⚠️ Disconnect the negative battery cable before unplugging ignition coils.
• ⚠️ Do not pull on the ignition coil wiring; pull only on the connector body.
• ⚠️ Keep dirt and debris out of the spark plug tubes.
• ⚠️ If the check engine light is flashing, avoid driving until the misfire is fixed to protect the catalytic converter.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 3/8-inch drive ratchet
• 3/8-inch drive 6-inch extension
• 10mm wrench
• Inch-pound torque wrench
• Flathead screwdriver
• Needle-nose pliers
• Compressed air duster
• OBD2 scan tool
• 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 small tube

Tip: Replace only the failed coil unless mileage is high or multiple coils are weak.

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📋 Before You Begin

• Park your Highlander on level ground.
• Shift to Park and set the parking brake.
• Let the engine cool completely.
• Open the hood and make sure the work area is well lit.
• If you have misfire codes, use an OBD2 scan tool to identify the affected cylinder before removing parts. An OBD2 scan tool reads fault codes from the vehicle’s computer.
• Cylinder numbering on the 2.7L inline-4 starts at the front of the engine timing-chain side and runs across the engine: cylinder 1, 2, 3, then 4.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Disconnect the Battery

• Put on safety glasses and nitrile gloves.
• Use a 10mm wrench to loosen the negative battery terminal clamp.
• Lift the negative cable off the battery post and move it aside so it cannot spring back.
• Negative terminal is marked with a minus sign.

Step 2: Remove the Engine Appearance Cover

• If equipped, gently lift the plastic engine cover upward by hand.
• If any fasteners are fitted, use a 10mm socket and 3/8-inch drive ratchet to remove them.
• Set the cover aside in a safe place.

Step 3: Locate the Ignition Coils

• The ignition coils are the four black plastic units mounted in a row on top of the engine.
• Each coil has one electrical connector and one small hold-down bolt.
• An ignition coil is a small transformer that creates the high voltage needed to fire the spark plug.

Step 4: Clean Around the Coil Area

• Use a compressed air duster to blow dirt away from the top of the ignition coils.
• Do not blow dirt directly into any open spark plug tube after a coil is removed.
• Clean first so debris cannot fall inside.

Step 5: Unplug the Ignition Coil Connector

• Press the connector release tab with your thumb.
• If the tab is stiff, use a flathead screwdriver very gently to help depress the lock.
• Pull the connector straight back from the coil.
• If needed, use needle-nose pliers only on the connector body, not the wires.
• Never yank the wiring harness.

Step 6: Remove the Coil Hold-Down Bolt

• Use a 10mm socket, 3/8-inch drive 6-inch extension, and 3/8-inch drive ratchet to remove the ignition coil bolt.
• Keep the bolt in a safe spot so it does not fall into the engine bay.

Step 7: Remove the Old Ignition Coil

• Grip the ignition coil by the top plastic body.
• Twist it gently left and right to loosen the rubber boot.
• Pull the coil straight up and out of the spark plug tube.
• The rubber boot is the long rubber sleeve that reaches down to the spark plug.
• Twist first, then pull upward.

Step 8: Prepare the New Ignition Coil

• Compare the new coil to the old coil by hand before installing it.
• Apply a tiny amount of dielectric grease inside the end of the rubber boot.
• Dielectric grease is a non-conductive silicone grease that helps keep moisture out and prevents the boot from sticking.
• Do not pack the boot full of grease.

Step 9: Install the New Ignition Coil

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

Step 10: Tighten the Coil Bolt

• Start the bolt by hand to avoid cross-threading.
• Use a 10mm socket, 3/8-inch drive 6-inch extension, and inch-pound torque wrench to tighten the bolt.
• Torque to 8 Nm (71 in-lbs)
• Do not overtighten. The coil body and valve cover mounting area can be damaged.

Step 11: Reconnect the Electrical Connector

• Push the connector onto the ignition coil by hand until it clicks.
• Lightly tug the connector body to confirm it is locked.

Step 12: Repeat for Additional Coils

• If replacing more than one coil, repeat Steps 5 through 11 for each coil.
• Use the same 10mm socket, 3/8-inch drive 6-inch extension, and inch-pound torque wrench for each hold-down bolt.
• Torque each coil bolt to 8 Nm (71 in-lbs)

Step 13: Reinstall the Engine Cover

• Place the engine cover back into position by hand.
• If bolts were removed, use a 10mm socket and 3/8-inch drive ratchet to snug them down.
• Do not overtighten plastic engine cover fasteners.

Step 14: Reconnect the Battery

• Place the negative battery cable back onto the battery post.
• Use a 10mm wrench to tighten the terminal clamp.
• Make sure the terminal does not rotate by hand after tightening.

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✅ After Repair

• Start your Highlander and let it idle for one to two minutes.
• Listen for smooth running and make sure the engine is not shaking.
• Use an OBD2 scan tool to clear misfire codes if the check engine light remains on.
• Take a short test drive with light throttle first.
• If the check engine light flashes again, stop driving and recheck coil connector seating and cylinder code location.
• If a misfire remains on the same cylinder after coil replacement, the spark plug, injector, wiring, or compression may need diagnosis.

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💰 DIY vs Shop Cost

Shop Cost: $180-$450 for one coil, or $500-$900 for all four coils

DIY Cost: $45-$120 per coil, or $180-$480 for all four coils

You Save: $100-$420 by doing it yourself!

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

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