🔧 Highlander - Ignition Coil Replacement

Your Highlander’s ignition coils sit on top of the spark plugs and provide the high voltage needed to fire each cylinder. Replacing a bad coil can fix misfires, rough idle, flashing check-engine light, and loss of power.

Difficulty Level: Intermediate | Estimated Time: 1.0–3.0 hours (front bank only: ~1 hour; all 6: ~2–3 hours)

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⚠️ Safety & Precautions

• ⚠️ Work on a cool engine; coils sit near hot parts.
• ⚠️ Disconnect the negative battery terminal if you’ll remove the intake manifold (recommended).
• ⚠️ Keep dirt out of spark plug holes; debris can damage the engine.
• ⚠️ Do not pull on wiring—press the connector lock tab first.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 12mm socket
• 14mm socket
• 3/8" drive ratchet
• 3/8" drive extensions (3" and 6")
• Torque wrench (5–30 Nm range)
• Flat-blade screwdriver
• Needle-nose pliers
• Trim clip removal tool
• Shop vacuum
• OBD-II 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: 1–6
• Upper intake manifold gasket set - Qty: 1 (needed if rear-bank coils are removed)
• Throttle body gasket - Qty: 1 (recommended if throttle body is removed)
• Dielectric grease - Qty: 1 small pack

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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 the rear bank (closest to the firewall), use a 10mm socket to disconnect the negative battery terminal and move it aside.
• If the check engine light is on, use an OBD-II scan tool to record codes (example: P0302). This helps you confirm which cylinder is misfiring before you swap parts.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Pull up firmly to pop the cover off its rubber grommets (no tools on most covers). If yours has bolts, remove them with a 10mm socket.

Step 2: Decide which bank you’re doing (front is easier)

• Front bank coils are at the front of the engine (closest to the radiator) and can be replaced directly.
• Rear bank coils are at the back (closest to the firewall) and typically require removing the upper intake manifold for access.

Step 3: Unplug the ignition coil connector

• Press the connector lock tab, then pull the connector straight off. If it’s stubborn, gently help it with a flat-blade screwdriver.
• Don’t pry on the wires.

Step 4: Remove the ignition coil hold-down bolt

• Remove the coil bolt using a 10mm socket and 3/8" drive ratchet.
• Set the bolt somewhere safe (dropping it can turn into a big job).

Step 5: Remove the coil

• Twist the coil slightly, then pull it straight up and out by hand.
• Use a shop vacuum to clean around the plug hole before reinstalling anything.

Step 6: Install the new coil

• Apply a tiny amount of dielectric grease inside the rubber boot (this helps prevent moisture and makes future removal easier).
• Push the coil straight down until you feel it seat on the spark plug.
• Install the hold-down bolt by hand first (to avoid cross-threading), then tighten with a torque wrench: Torque to 9 Nm (80 in-lbs).
• Reconnect the electrical connector until it clicks.

Step 7 (Rear bank only): Remove the upper intake manifold for access

• Disconnect the negative battery cable using a 10mm socket (if not already done).
• Loosen the air intake tube clamps with a flat-blade screwdriver and remove the tube.
• Disconnect vacuum/PCV hoses using needle-nose pliers where clamps are used; label hoses if needed.
• Unbolt the upper intake manifold fasteners using a 12mm socket and 3/8" drive extensions.
• Lift the manifold off carefully and cover the intake ports with a clean cloth so nothing falls in.
• Replace the rear-bank coils using Steps 3–6.
• Install new upper intake manifold gaskets, then reinstall the manifold and torque the fasteners with a torque wrench: Torque to 21 Nm (15 ft-lbs).

Step 8: Reassemble and reinstall the engine cover

• Reconnect all hoses and connectors you removed.
• Reinstall the air intake tube and tighten clamps with a flat-blade screwdriver.
• Reconnect the negative battery terminal using a 10mm socket (if disconnected).
• Reinstall the engine cover.

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✅ After Repair

• Use an OBD-II scan tool to clear codes and confirm the misfire does not return.
• Start the engine and listen for smooth idle. If it runs rough, shut it off and re-check coil connectors and intake hoses.
• Test drive 10–15 minutes, then re-scan for pending codes.
• If you removed the intake manifold, do a quick check for any hissing sounds (vacuum leak) and make sure idle is stable.

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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: $60–$420 (parts only, 1–6 coils + gaskets if needed)

You Save: $190–$330+ by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.0–3.0 hours.

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