🔧 4Runner - Spark Plug Replacement

Your 4Runner uses six long-life iridium spark plugs, one for each cylinder. Replacement requires removing the ignition coils, cleaning each plug well, and installing the new plugs without damaging the aluminum cylinder-head threads.

Difficulty Level: Intermediate | Estimated Time: 1.5-2.5 hours

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⚠️ Safety & Precautions

• Let the engine become completely cold before removing the spark plugs.
• Wear safety glasses when blowing debris away from the plug wells.
• Never allow dirt, tools, or loose hardware to fall into an open spark-plug hole.
• Start every new plug by hand. Cross-threading can require expensive cylinder-head repair.
• Do not apply anti-seize compound to the plated threads of the specified iridium plugs.
• Disconnect the negative battery terminal before unplugging the ignition coils.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 12mm socket
• 16mm 5/8-inch spark-plug socket
• 3/8-inch drive ratchet
• 3/8-inch drive 3-inch extension
• 3/8-inch drive 6-inch extension
• 3/8-inch drive universal-joint extension
• 3/8-inch drive torque wrench rated 10-80 ft-lbs
• Inch-pound torque wrench rated 50-250 in-lbs
• Flat-blade screwdriver
• Needle-nose pliers
• Compressed-air blow gun with regulated air supply
• 3/8-inch inside-diameter rubber hose, 8 inches long
• Fender cover
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs, Denso SK16HR11 or exact equivalent - Qty: 6
• Dielectric ignition-boot grease - Qty: 1 small tube

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📋 Before You Begin

• Park your 4Runner on level ground, select Park, apply the parking brake, and open the hood.
• Allow the engine to cool completely. Aluminum cylinder-head threads are easier to damage while hot.
• Use a 10mm socket to disconnect the negative battery terminal. Move the cable aside so it cannot touch the post.
• Place a fender cover over the painted bodywork.
• Check the new plug markings. The specified plug gap is approximately 1.0-1.1mm (0.039-0.043 inch). Do not force a wire gauge between the delicate iridium electrodes or bend them.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the Engine Cover

• Lift the front of the plastic engine cover upward to release its retainers, then remove the cover.
• If a retaining fastener is fitted, remove it first with a 10mm socket.
• Place the cover away from the work area.

Step 2: Remove the Air-Intake Tube

• Use a 10mm socket or flat-blade screwdriver to loosen the clamps at the air-filter housing and throttle-body ends of the intake tube.
• Use needle-nose pliers to release any spring clamp, then disconnect the attached breather hose.
• Unclip any wiring retainer attached to the tube. Carefully remove the intake tube without pulling on electrical wires.
• Cover the exposed throttle-body opening with a clean, lint-free cloth.

Step 3: Create Access to the Ignition Coils

• Use a 10mm or 12mm socket, as applicable, to remove the small wiring-harness and hose brackets blocking the coils.
• Move only the brackets and harness sections needed for access. Do not stretch wires or disconnect fuel lines.
• Keep each bracket and bolt together so it returns to its original location.
• Photograph bracket positions before removal.

Step 4: Remove the First Ignition Coil

• Work on one cylinder at a time so connectors and coils cannot be mixed up.
• Press the electrical connector lock and pull the connector straight off. Do not pull on the wires.
• Use a 10mm socket and ratchet to remove the coil retaining bolt.
• Twist the coil gently, then pull it straight out. An ignition coil is the narrow electrical unit sitting directly above each spark plug.

Step 5: Clean the Spark-Plug Well

• Put on safety glasses.
• Use the compressed-air blow gun to remove dirt from the spark-plug well before loosening the plug.
• Keep your face away from the well while using compressed air.
• Inspect the coil boot for oil, cracking, swelling, or burn marks. Oil in the well indicates a sealing problem that should be repaired.

Step 6: Remove the Old Spark Plug

• Fit the 16mm 5/8-inch spark-plug socket to the 6-inch extension and 3/8-inch ratchet. Use the universal-joint extension only where clearance requires it.
• Turn the spark plug counterclockwise slowly. Stop if it binds severely rather than loosening smoothly.
• Lift the old plug from the well with the spark-plug socket.
• Check for heavy oil deposits, broken ceramic, damaged threads, or an unusually white or black electrode.

Step 7: Install the New Spark Plug by Hand

• Confirm the new plug matches the old plug in thread length and seat design.
• Insert the new plug into the 3/8-inch rubber hose. The hose acts as a flexible hand-starting tool and slips if the plug begins cross-threading.
• Lower the plug straight into the well and turn the hose clockwise until the gasket reaches the cylinder head.
• Do not use anti-seize on the spark-plug threads.
• If the plug does not turn easily by hand, remove it and start again.

Step 8: Torque the Spark Plug

• Attach the 16mm 5/8-inch spark-plug socket and extension to the 3/8-inch drive torque wrench.
• Tighten the spark plug to 18 Nm (13 ft-lbs).
• Keep the extension aligned with the plug while tightening. Do not use an impact wrench.

Step 9: Reinstall the Ignition Coil

• Apply a very small film of dielectric ignition-boot grease inside the opening at the end of the coil boot. Keep grease away from the plug terminal and threads.
• Push the coil straight down until it is fully seated on the spark plug.
• Install the coil bolt with a 10mm socket and inch-pound torque wrench. Torque to 10 Nm (89 in-lbs).
• Reconnect the electrical connector until its lock clicks.

Step 10: Replace the Remaining Five Plugs

• Repeat Steps 4 through 9 for each remaining cylinder.
• Use the 3-inch extension or universal-joint extension where the brake-booster area limits access on the driver side.
• Clean every well before removing its spark plug.
• Verify that all six coil connectors are fully locked before continuing.

Step 11: Reinstall Brackets and Intake Components

• Return every wiring and hose bracket to its original position using the 10mm or 12mm socket.
• Tighten small M6 bracket bolts to 10 Nm (89 in-lbs) unless the removed fastener or bracket uses a different specified value.
• Remove the cloth from the throttle body and reinstall the air-intake tube.
• Reconnect the breather hose and wiring retainers. Tighten both intake clamps securely with the 10mm socket or flat-blade screwdriver.

Step 12: Reinstall the Engine Cover and Battery Cable

• Align the engine-cover retainers and press the cover firmly into place.
• If equipped with a cover fastener, install it using the 10mm socket and tighten it only until snug.
• Reconnect the negative battery terminal using the 10mm socket. Torque to 5.4 Nm (48 in-lbs).

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✅ After Repair

• Check the engine bay for tools, loose bolts, disconnected hoses, and unplugged ignition coils.
• Start the engine and let it idle. It may briefly idle differently while electronic settings relearn after battery disconnection.
• Listen for a steady idle and confirm that the check-engine light does not flash.
• If the engine misfires, shut it off immediately and recheck all six coil connectors, coil seating, and intake connections.
• Confirm the air-intake tube is sealed at both ends. An intake leak can cause poor running or warning lights.
• Reset the clock and radio preferences if they were lost during battery disconnection.

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💰 DIY vs Shop Cost

Shop Cost: $350-$650 (parts + labor)

DIY Cost: $70-$140 (parts only)

You Save: $210-$580 by doing it yourself!

Imported-part pricing and labor around Sonīpat can vary considerably. This repair takes a shop approximately 1.5-2.0 hours.

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🎯 Ready to get started?

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