🔧 4Runner - Spark Plug Replacement

Your 4Runner uses 6 spark plugs (one per cylinder). Replacing them restores smooth starting, idle quality, and fuel economy, and helps prevent misfires as mileage builds.

Difficulty Level: Intermediate | Estimated Time: 2.0-4.0 hours

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⚠️ Safety & Precautions

• Work on a fully cool engine to avoid burns and to protect aluminum threads.
• Disconnect the negative battery cable before unplugging sensors/throttle body connectors.
• Do not blow debris into the spark plug holes; dirt can damage the engine.
• Do not use anti-seize on the new plugs; Toyota plugs are plated and torque changes with anti-seize.
• Use a torque wrench (a tool that tightens to an exact setting) to avoid stripping threads.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• 10mm socket
• 12mm socket
• 3/8" ratchet
• 3/8" torque wrench (10-80 ft-lbs range)
• 1/4" torque wrench (in-lb range)
• 5/8" spark plug socket
• 3/8" extension set (3", 6", 10")
• 3/8" universal joint adapter
• Flathead screwdriver
• Needle-nose pliers
• Trim clip removal tool
• Compressed air blow gun
• Shop vacuum
• Magnetic pickup tool
• Clean rags

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (iridium, correct OEM equivalent) - Qty: 6
• Upper intake manifold gasket set - Qty: 1
• Throttle body gasket - Qty: 1
• 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 cool completely (at least 1 hour).
• Disconnect the negative battery terminal using a 10mm socket and isolate the cable so it can’t spring back.
• Label connectors with masking tape if you’re new to this. Photos help a lot.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Lift off the plastic engine cover by pulling it upward firmly with both hands.

Step 2: Remove the air intake tube

• Loosen the hose clamps using a flathead screwdriver.
• Unclip or remove any attached small hoses/sensors carefully (use needle-nose pliers for spring clamps).
• Remove the intake tube and set it aside with its clamps.

Step 3: Replace the 3 easy-to-reach spark plugs (passenger-side bank)

• Unplug one ignition coil connector at a time (press the tab, then pull).
• Remove the coil bolt using a 10mm socket and pull the coil straight up.
• Blow debris away from the spark plug well using compressed air blow gun.
• Remove the spark plug using a 5/8" spark plug socket, 3/8" ratchet, and extension.
• Install the new spark plug by hand first using the spark plug socket and extension (no ratchet yet) to prevent cross-threading.
• Tighten the spark plug using a 3/8" torque wrench: Torque to 18 Nm (13 ft-lbs).
• Apply a tiny smear of dielectric grease inside the coil boot (this helps prevent moisture-related misfires).
• Reinstall the coil and tighten the coil bolt with a 1/4" torque wrench: Torque to 10 Nm (89 in-lbs).
• Reconnect the coil connector.
• Repeat for the other 2 plugs on this side.

Step 4: Remove the throttle body (to access the intake manifold)

• Unplug the throttle body electrical connector.
• Remove the throttle body mounting bolts using a 10mm socket.
• Lift the throttle body off and set it aside (do not force the wiring).
• Remove and discard the old throttle body gasket.
• Cover the intake opening with a clean rag to keep hardware out.
• When reinstalling later, tighten throttle body bolts with a 1/4" torque wrench: Torque to 10 Nm (89 in-lbs).

Step 5: Remove the upper intake manifold (to reach the driver-side plugs)

• Disconnect any vacuum/PCV hoses attached to the upper intake using needle-nose pliers as needed.
• Unplug any connectors that prevent lifting the manifold (use your photos/labels).
• Remove the upper intake manifold bolts/nuts using a 12mm socket and 3/8" ratchet.
• Lift the upper intake manifold off carefully and set it on a clean surface.
• Remove and discard the old upper intake manifold gaskets.
• Cover the lower intake ports with clean rags. Do not drop anything inside.

Step 6: Replace the 3 driver-side spark plugs

• Remove each ignition coil connector and coil bolt using a 10mm socket, then pull the coil straight out.
• Blow out each spark plug well using compressed air blow gun.
• Remove each plug using a 5/8" spark plug socket, extension, and a 3/8" universal joint adapter (a swivel that helps at angles).
• Hand-thread each new plug first, then tighten with a 3/8" torque wrench: Torque to 18 Nm (13 ft-lbs).
• Reinstall coils and tighten coil bolts with a 1/4" torque wrench: Torque to 10 Nm (89 in-lbs).
• Reconnect coil connectors.

Step 7: Reinstall the upper intake manifold with new gaskets

• Remove the rags covering the intake ports and verify nothing fell in.
• Install the new upper intake manifold gaskets in the correct positions.
• Set the manifold back in place.
• Install bolts/nuts finger-tight first, then tighten evenly using a 12mm socket.
• Final tighten using a 3/8" torque wrench: Torque to 21 Nm (15 ft-lbs).
• Reconnect all hoses and electrical connectors you removed.

Step 8: Reinstall the throttle body with a new gasket

• Remove the rag from the opening.
• Install the new throttle body gasket.
• Reinstall the throttle body and tighten bolts using a 1/4" torque wrench: Torque to 10 Nm (89 in-lbs).
• Reconnect the throttle body electrical connector.

Step 9: Reinstall the air intake and engine cover

• Reinstall the intake tube and tighten clamps using a flathead screwdriver.
• Reinstall any clips using a trim clip removal tool as needed.
• Press the engine cover back into place.

Step 10: 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 2 minutes; it may idle slightly high at first.
• Listen for vacuum leaks (a loud hissing) around the intake manifold area.
• Verify there’s no check engine light and the engine runs smoothly.
• Take a short test drive and recheck for any loose clamps/hoses afterward.

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💰 DIY vs Shop Cost

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

DIY Cost: $60-$140 (parts only)

You Save: $210-$590 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2.0-3.5 hours.

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🎯 Ready to get started?

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