🔧 4Runner - Spark Plug Replacement

Your 4Runner uses one spark plug per cylinder (6 total). The front three are easy to reach, but the rear three sit under the upper intake plenum, so you’ll remove that to access them.

Difficulty Level: Advanced | Estimated Time: 2.5-4.5 hours

Assumption: 4.0L V6 rear-bank plugs require upper intake plenum removal.

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⚠️ Safety & Precautions

• ⚠️ Do this on a fully cold engine to prevent burns and thread damage.
• ⚠️ Disconnect the negative battery cable before unplugging coils or throttle body.
• ⚠️ Keep dirt out of the intake; cover ports with clean rags immediately.
• ⚠️ Hand-start spark plugs; cross-threading can ruin the cylinder head.
• ⚠️ Do not overtighten plugs; aluminum threads strip easily.

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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" drive ratchet
• 3/8" drive torque wrench (10–30 ft-lbs range)
• 1/4" drive torque wrench (50–120 in-lbs range)
• 5/8" (16mm) spark plug socket
• 3/8" drive extension set (3", 6", 10")
• 3/8" drive wobble extension
• 3/8" drive universal joint
• Flathead screwdriver (medium)
• Pliers (hose clamp)
• Trim clip removal tool
• Pick tool (small)
• Compressed air blow gun
• Shop vacuum
• Shop rags
• Flashlight
• Magnetic pickup tool

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs (OEM-equivalent) - Qty: 6
• Upper intake plenum gasket set - Qty: 1
• Throttle body gasket - Qty: 1
• Dielectric grease (spark plug/coil boots) - 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.
• Disconnect the negative battery terminal using a 10mm socket and move the cable aside.
• Use a flashlight and take quick photos of hose routing and connector locations.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Pull straight up to pop off the engine cover (rubber grommets hold it).

Step 2: Remove the intake tube and air ducting

• Remove any clips with a trim clip removal tool.
• Loosen hose clamps using a flathead screwdriver (medium).
• Disconnect small hoses using pliers (hose clamp), then lift the intake tube out.
• Tip: Twist hoses to break them loose.

Step 3: Replace the front-bank spark plugs (easier side)

• For each front cylinder, blow debris away with a compressed air blow gun.
• Unplug the ignition coil connector; use a pick tool (small) only to release the lock.
• Remove the coil bolt using a 10mm socket, then pull the coil out.
• Blow out the spark plug well with a compressed air blow gun.
• Remove the plug using a 5/8" (16mm) spark plug socket, 3/8" drive extension set, and 3/8" drive ratchet.
• Install the new plug by hand first using the spark plug socket and an extension (no ratchet yet).
• Final tighten with a 3/8" drive torque wrench (10–30 ft-lbs range): Torque to 18 Nm (13 ft-lbs).
• Apply a small dab of dielectric grease (spark plug/coil boots) inside the coil boot.
• Reinstall the coil and tighten the coil bolt with a 1/4" drive torque wrench (50–120 in-lbs range): Torque to 10 Nm (89 in-lbs).

Step 4: Remove the throttle body (move aside)

• Unplug the throttle body connector using a pick tool (small) to release the lock.
• Remove the throttle body mounting bolts using a 10mm socket.
• Carefully move the throttle body aside and support it with shop rags (do not stretch wiring).
• Remove and discard the old throttle body gasket.
• When reinstalling later: Torque to 10 Nm (89 in-lbs).

Step 5: Remove the upper intake plenum (to reach the rear plugs)

• Disconnect vacuum/PCV/EVAP hoses with pliers (hose clamp) and a flathead screwdriver (medium) as needed.
• Unplug any connectors attached to the plenum; use a pick tool (small) to release locks.
• Remove the plenum nuts/bolts using a 12mm socket and 3/8" drive ratchet.
• Lift the plenum straight up and off.
• Immediately cover the intake ports with shop rags.
• Remove and discard the old upper intake plenum gasket set.
• Tip: Count bolts so none go missing.

Step 6: Replace the rear-bank spark plugs (harder side)

• Use a shop vacuum to remove loose dirt around the rear coils before you pull them.
• Blow around each coil and plug well using a compressed air blow gun.
• Unplug each coil, remove the coil bolt with a 10mm socket, and pull the coil out.
• Remove each plug using a 5/8" (16mm) spark plug socket, 3/8" drive wobble extension, and 3/8" drive ratchet.
• If you need more angle, use a 3/8" drive universal joint.
• Install each new plug by hand first, then torque with a 3/8" drive torque wrench (10–30 ft-lbs range): Torque to 18 Nm (13 ft-lbs).
• Apply a small dab of dielectric grease (spark plug/coil boots) inside each coil boot.
• Reinstall coils and torque each coil bolt with a 1/4" drive torque wrench (50–120 in-lbs range): Torque to 10 Nm (89 in-lbs).

Step 7: Reinstall the upper intake plenum

• Remove all shop rags from the intake ports (double-check every port).
• Install the new upper intake plenum gasket set in place.
• Set the plenum down carefully and hand-start all nuts/bolts.
• Tighten evenly with a 12mm socket, then final torque with a 3/8" drive torque wrench (10–30 ft-lbs range): Torque to 21 Nm (15 ft-lbs).
• Reconnect every hose and connector you removed.

Step 8: Reinstall the throttle body

• Install a new throttle body gasket.
• Reinstall throttle body bolts using a 10mm socket, then final torque: Torque to 10 Nm (89 in-lbs).
• Plug the throttle body connector back in until it clicks.

Step 9: Reinstall intake tube and engine cover

• Reinstall the intake tube and tighten clamps using a flathead screwdriver (medium).
• Reinstall any clips with a trim clip removal tool.
• Press the engine cover back onto the grommets.

Step 10: Reconnect the battery

• Reconnect the negative battery terminal using a 10mm socket.
• If you dropped any hardware, retrieve it using a magnetic pickup tool before starting.

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✅ After Repair

• Start the engine and let it idle for 2–3 minutes. A slightly rough idle for a few seconds can be normal after intake work.
• Listen for a hissing sound near the plenum/throttle body (this can indicate a vacuum leak).
• If the check engine light comes on, recheck coil connectors and any unplugged hoses first.
• Take a 10–15 minute test drive, then do a quick under-hood check for loose clamps or hoses.

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💰 DIY vs Shop Cost

Shop Cost: ₹9,000-₹20,000 (parts + labor)

DIY Cost: ₹3,500-₹10,000 (parts only)

You Save: ₹5,500-₹10,000 by doing it yourself!

Shop labor rates vary but typically run ₹800-₹1,500/hour. This repair takes a shop approximately 2.5-4.0 hours.

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