🔧 MDX - Spark Plug Replacement

On your MDX, the front-bank spark plugs are easy to reach, but the rear-bank plugs sit under the upper intake manifold. You’ll remove a few covers and ignition coils, replace all 6 plugs, then reassemble with new intake gaskets to prevent vacuum leaks.

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

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⚠️ Safety & Precautions

• ⚠️ Work on a fully cool engine to avoid burns and damaged threads.
• ⚠️ Disconnect the negative battery cable before unplugging throttle body/engine sensors.
• ⚠️ Keep dirt out of the intake—cover open ports with clean shop towels.
• ⚠️ Do not use anti-seize on Acura/Honda plated spark plug threads unless the plug maker specifically requires it.
• ⚠️ If you drop anything into the intake runners, do not crank the engine.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• 3/8" drive ratchet
• 3/8" drive torque wrench (10-30 ft-lbs range)
• 10mm socket
• 12mm socket
• 8mm socket
• 6" extension (3/8" drive)
• 10" extension (3/8" drive)
• 5/8" spark plug socket (3/8" drive, rubber insert or магнит type)
• Flat trim tool
• Needle-nose pliers
• Pick tool
• Small flashlight
• Compressed air blow gun
• Shop towels

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs (OEM-type) - Qty: 6
• Upper intake manifold gasket set - Qty: 1
• Throttle body gasket - Qty: 1
• Dielectric grease (for coil boots) - Qty: 1

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📋 Before You Begin

• 🅿️ Park on level ground, shift to Park, and set the parking brake.
• 🔋 Use a 10mm socket to disconnect the negative battery terminal and tuck it aside.
• 🧼 Blow off loose dirt around the engine with compressed air blow gun so debris doesn’t fall into the intake or plug wells.
• 🧠 A torque wrench is a tool that tightens bolts to an exact spec so you don’t strip threads.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover and air ducting

• Remove the plastic engine cover by pulling it up (it’s held by grommets). Use a flat trim tool if needed.
• Loosen the intake tube clamps using an 8mm socket.
• Disconnect any attached breather/PCV hoses with needle-nose pliers and set the intake tube/ducting aside.

Step 2: Replace the front-bank spark plugs (radiator side)

• Unplug each ignition coil connector by lifting the lock tab using a pick tool, then pulling the connector straight off.
• Remove each ignition coil hold-down bolt with a 10mm socket.
• Twist and pull the coil straight up to remove it. Wiggle gently—don’t yank the wiring.
• Blow out each spark plug well using a compressed air blow gun.
• Remove the spark plug using a 5/8" spark plug socket, 10" extension, and 3/8" drive ratchet.
• Install the new plug by hand first using the spark plug socket and extension (no ratchet) to avoid cross-threading.
• Tighten each plug with a 3/8" torque wrench: Torque to 18 N·m (13 ft-lbs).
• Apply a small smear of dielectric grease inside the tip of each coil boot (not on the plug threads).
• Reinstall coils and tighten coil bolts with a 10mm socket: Torque to 12 N·m (9 ft-lbs).
• Reconnect coil connectors until they click.

Step 3: Remove the upper intake manifold (to access rear-bank plugs)

• Disconnect the throttle body electrical connector using a pick tool to lift the lock, then pull straight off.
• Disconnect any vacuum/PCV hoses attached to the upper intake using needle-nose pliers. Take a quick phone photo so hoses go back correctly.
• Remove the upper intake manifold fasteners using a 12mm socket and 3/8" drive ratchet.
• Lift the upper intake manifold off carefully.
• Immediately stuff each exposed intake port with clean shop towels.

Step 4: Replace the rear-bank spark plugs (firewall side)

• Repeat the same coil removal process using a 10mm socket and pick tool.
• Blow out plug wells with the compressed air blow gun.
• Remove and install spark plugs using the 5/8" spark plug socket, extensions, and 3/8" drive ratchet.
• Tighten each rear plug with a 3/8" torque wrench: Torque to 18 N·m (13 ft-lbs).
• Reinstall coils and tighten coil bolts: Torque to 12 N·m (9 ft-lbs).
• Reconnect all rear coil connectors until they click.

Step 5: Reinstall the upper intake manifold with new gaskets

• Remove the old upper intake manifold gaskets with a pick tool.
• Install the new gaskets, making sure they sit fully in their grooves.
• Remove the shop towels from the intake ports.
• Set the upper intake manifold back in place.
• Install the fasteners finger-tight first, then tighten evenly using a 12mm socket.
• Final tighten with a 3/8" torque wrench: Torque to 22 N·m (16 ft-lbs).
• If the throttle body was loosened/removed, install a new throttle body gasket and tighten bolts using a 10mm socket: Torque to 12 N·m (9 ft-lbs).
• Reconnect all vacuum/PCV hoses using needle-nose pliers and reconnect the throttle body connector.

Step 6: Reinstall intake tube and engine cover

• Reinstall intake ducting and tighten clamps with an 8mm socket.
• Reinstall the engine cover by pressing it down into the grommets.
• Reconnect the negative battery terminal using a 10mm socket.

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✅ After Repair

• 🔎 Start the engine and let it idle. Listen for hissing (vacuum leak) and watch for a check engine light.
• 🧪 If the idle is rough after battery disconnect, let it idle with all accessories off for about 5 minutes once warmed up.
• 🛣️ Take a short test drive and recheck for warning lights.

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💰 DIY vs Shop Cost

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

DIY Cost: $90-$220 (parts only)

You Save: $360-$630 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2.5-4.0 hours.

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🎯 Ready to get started?

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