🔧 Highlander - Ignition Coil Replacement

Ignition coils sit on top of the spark plugs and create the high voltage needed to fire each cylinder. On your Highlander, the front bank is easy to reach, but the rear bank coils require removing the upper intake manifold for access.

Difficulty Level: Intermediate | Estimated Time: 1.5-3.5 hours

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⚠️ Safety & Precautions

• ⚠️ Work on a cold engine to avoid burns and damaged plastic connectors.
• ⚠️ Disconnect the negative battery cable before unplugging coils (prevents accidental shorts and false codes).
• ⚠️ Keep dirt out of the spark plug tubes; blow debris away before removing a coil.
• ⚠️ If removing the intake manifold, do not drop bolts into the intake ports.

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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)
• Trim clip remover
• Needle-nose pliers
• Flathead screwdriver
• Compressed air blow gun
• Shop towels
• Nitrile gloves
• Safety glasses
• OBD2 scan tool

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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 doing rear bank
• Throttle body gasket - Qty: 1 Recommended if throttle body is removed
• Dielectric grease - Qty: 1

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📋 Before You Begin

• Park on level ground, shift to Park, and set the parking brake.
• Open the hood and let the engine fully cool.
• Use a 10mm socket to disconnect the negative battery terminal and isolate it so it can’t spring back.
• If you have a misfire, use an OBD2 scan tool to note the code (example: P0302 = cylinder 2). This helps you replace only the bad coil if you want.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Pull up firmly on the plastic engine cover to release the grommets (use a trim clip remover if it’s stubborn).
• Set the cover aside.

Step 2: Decide which bank you’re servicing

• Front bank coils: You can see them at the front of the engine—go to Step 3.
• Rear bank coils: They are against the firewall—skip to Step 6.

Step 3: Unplug the coil connector (front bank)

• Press the connector lock tab and pull the plug straight off the coil.
• If the tab is hard to press, gently help it with a flathead screwdriver (don’t break the tab).

Step 4: Remove the coil hold-down bolt (front bank)

• Use a 10mm socket with a 3" extension to remove the coil bolt.
• Set the bolt aside where it won’t get lost.

Step 5: Remove and replace the coil (front bank)

• Before pulling the coil, use a compressed air blow gun to blow dirt away from the coil area.
• Twist the coil slightly, then pull straight up to remove it (the rubber boot seals to the plug).
• Put a pea-sized amount of dielectric grease inside the new coil boot. Helps prevent moisture and sticking
• Install the new coil by pushing straight down until fully seated.
• Reinstall the bolt using a 10mm socket, then Torque to 9 N·m (80 in-lb).
• Reconnect the electrical plug until it clicks.

Step 6: Remove air intake ducting (rear bank access)

• Use a flathead screwdriver or 10mm socket to loosen the hose clamps on the intake duct.
• Disconnect any small vacuum/vent hoses using needle-nose pliers (pinch spring clamps and slide them back).
• Lift the duct out and set it aside.

Step 7: Remove the upper intake manifold (rear bank access)

• Disconnect visible vacuum/EVAP hoses and electrical connectors on the manifold (use a flathead screwdriver only if needed to release locks).
• Remove manifold mounting bolts/nuts using a 12mm socket with a 6" extension.
• Lift the upper intake manifold off carefully.
• Immediately place shop towels into the exposed intake ports so nothing can fall in.
• Remove and discard the old upper intake manifold gaskets (do not reuse).

Step 8: Replace the rear bank coils

• One coil at a time, unplug the connector (press tab and pull).
• Use a 10mm socket to remove the hold-down bolt.
• Use compressed air blow gun to clear debris, then pull the coil straight up.
• Apply a small amount of dielectric grease inside the new coil boot and install the new coil.
• Reinstall the bolt and Torque to 9 N·m (80 in-lb).
• Reconnect each coil connector until it clicks.

Step 9: Reinstall the upper intake manifold

• Remove the shop towels from the intake ports.
• Install new upper intake manifold gaskets in the grooves (make sure they sit flat).
• Set the manifold back in place carefully without pinching any wiring.
• Install the bolts/nuts finger-tight first using a 12mm socket, then tighten evenly in a crisscross pattern.
• Torque to 21 N·m (15 ft-lb).
• Reconnect all hoses and connectors you removed.

Step 10: Reinstall intake ducting and engine cover

• Reinstall the air intake duct and tighten clamps using a 10mm socket or flathead screwdriver.
• Reinstall any hoses/clips removed.
• Press the engine cover back onto its mounting grommets.

Step 11: Reconnect the battery

• Reconnect the negative battery terminal using a 10mm socket.

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✅ After Repair

• Start the engine and let it idle for 1-2 minutes. It should run smooth with no flashing check engine light.
• Use an OBD2 scan tool to clear misfire codes if present, then recheck for returning codes after a short drive.
• Do a short test drive and recheck for vacuum leaks (hissing sound) if the intake manifold was removed.

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💰 DIY vs Shop Cost

Shop Cost: $350-$900 (parts + labor)

DIY Cost: $60-$420 (parts only)

You Save: $290-$480 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.5-3.0 hours.

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🎯 Ready to get started?

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