🔧 Spark Plugs - Replacement

Your Sienna uses six spark plugs, and the rear bank sits under the intake manifold. The job is straightforward but takes patience, because the upper intake has to come off to reach all six plugs cleanly.

Difficulty Level: Intermediate | Estimated Time: 3-5 hours

---

⚠️ Safety & Precautions

• Let the engine cool completely before starting. Hot intake parts and coils can burn you.
• Disconnect the negative battery cable before removing the intake manifold.
• Keep dirt out of the intake ports. Do not let anything fall into the engine.
• Use only the correct iridium spark plugs for this engine.
• Do not over-tighten plugs. The cylinder head is aluminum and can be damaged.
• Work one cylinder at a time.

---

🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 12mm socket
• 14mm socket
• 3/8-inch ratchet
• 3/8-inch extension set
• 3/8-inch swivel joint
• Torque wrench
• Spark plug socket
• Flat-blade trim tool
• Needle-nose pliers
• Gloves
• Safety glasses
• Fender cover

---

🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs - Qty: 6
• Intake manifold gasket set - Qty: 1
• Throttle body gasket - Qty: 1

---

📋 Before You Begin

• Park on level ground and set the parking brake.
• Let the engine cool fully.
• Disconnect the negative battery cable with a 10mm socket.
• Remove loose items from the engine bay so nothing falls into the intake.

---

🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover and intake duct

• Pull up on the engine cover to remove it.
• Use a flat-blade trim tool or 10mm socket to loosen the air intake duct clamps and remove the ducting.
• Disconnect any small hoses or connectors attached to the intake tube.

Step 2: Remove the throttle body and upper intake manifold

• Use a 10mm socket and extensions to remove the throttle body fasteners if needed for access.
• Unplug the throttle body connector carefully.
• Use a 10mm socket and 3/8-inch extension set to remove the upper intake manifold bolts.
• Lift the intake manifold off straight and keep debris out of the ports.
• Stuff clean lint-free towels in the intake ports.

Step 3: Remove the ignition coils

• Use a 10mm socket to remove each ignition coil hold-down bolt.
• Disconnect each coil connector and label them if needed.
• Pull each coil straight out with a gentle twist.

Step 4: Remove the old spark plugs

• Use a spark plug socket, extension set, and swivel joint to remove each plug.
• Turn each plug slowly to avoid cross-threading damage.
• Compare the old plugs for heavy oil, white deposits, or uneven wear.

Step 5: Install the new spark plugs

• Check the gap only if the plug manufacturer says it is allowed.
• Thread each new plug in by hand first using the spark plug socket.
• Tighten each plug with a torque wrench to 18 Nm (13 ft-lbs).
• Hand-start every plug first.

Step 6: Reinstall the ignition coils

• Push each coil fully into place.
• Reinstall the coil bolts with a 10mm socket.
• Torque to 9 Nm (80 in-lbs).
• Reconnect each coil connector until it clicks.

Step 7: Reinstall the intake manifold and throttle body

• Remove the towels from the intake ports.
• Install the new intake manifold gasket set.
• Set the manifold in place carefully by hand.
• Use a 10mm socket and torque wrench to tighten the manifold bolts evenly in steps.
• Torque to 21 Nm (15 ft-lbs).
• Reinstall the throttle body with the new gasket and tighten its fasteners to 10 Nm (89 in-lbs).

Step 8: Reinstall the intake duct and engine cover

• Reconnect all hoses and clamps.
• Reinstall the intake duct and tighten the clamps with a flat-blade trim tool or 10mm socket.
• Press the engine cover back into place.
• Reconnect the negative battery cable with a 10mm socket.

---

✅ After Repair

• Start the engine and let it idle.
• Listen for vacuum leaks or rough running.
• Check that the check engine light stays off.
• Take a short test drive and confirm smooth acceleration.
• If the idle is rough, recheck all coil connectors and intake connections.

---

💰 DIY vs Shop Cost

Shop Cost: $450-$850 (parts + labor)

DIY Cost: $90-$180 (parts only)

You Save: $360-$670 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 3-5 hours.

---

🎯 Ready to get started?

HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.