🔧 RDX - Spark Plug Replacement

On your RDX, the front 3 spark plugs are easy to access, but the rear 3 sit under the upper intake manifold (the top aluminum “air passage” that feeds the engine). This job is mostly careful disassembly, keeping dirt out, and torquing the new plugs correctly.

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

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⚠️ Safety & Precautions

• ⚠️ Work on a cool engine to avoid burns and prevent thread damage in the cylinder heads.
• ⚠️ Disconnect the negative battery cable to prevent accidental shorts and misfires while connectors are unplugged.
• ⚠️ Keep debris out of the intake ports; stuff clean rags in openings as soon as the manifold is lifted.
• ⚠️ Do not use anti-seize on modern plated spark plugs unless the plug maker explicitly requires it.
• ⚠️ Use a torque wrench—over-tightening can strip the aluminum threads.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 12mm socket
• 14mm socket
• 3/8" drive ratchet
• 3/8" drive torque wrench (10-60 Nm range)
• 5/8" spark plug socket (rubber insert)
• 3/8" drive extension set (3", 6", 10")
• 3/8" drive universal joint
• Flat trim tool
• Needle-nose pliers
• Pick tool
• Shop vacuum
• Compressed air blow gun
• Painter’s tape and marker
• Fender cover
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (laser iridium type, pre-gapped) - 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 fully.
• Use a 10mm socket to disconnect the negative battery cable and tuck it aside so it can’t spring back.
• Use painter’s tape and marker to label any hoses/connectors you’re nervous about mixing up.
• Take photos before unplugging anything.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover and clear the work area

• Lift off the plastic engine cover (it pulls upward; use a flat trim tool if needed).
• Use a shop vacuum to remove loose dirt around the top of the engine.

Step 2: Replace the FRONT bank spark plugs (easy access)

• Unplug the ignition coil connectors by pressing the lock tab; use a pick tool gently if the tab is stuck. (An ignition coil is the “stick-like” part that makes spark for that cylinder.)
• Use a 10mm socket to remove each ignition coil hold-down bolt.
• Twist and pull the coil upward to remove it; set it aside in order.
• Blow out the spark plug well using compressed air blow gun so dirt can’t fall into the engine.
• Remove the spark plug using a 5/8" spark plug socket, extension, and ratchet.
• Install the new spark plug by hand first using the spark plug socket and extension (no ratchet at first) to avoid cross-threading.
• Tighten with a torque wrench: Torque to 18 Nm (13 ft-lbs).
• Apply a tiny dab of dielectric grease inside the coil boot (the rubber end) and reinstall the coil.
• Reinstall the coil bolt with a 10mm socket: Torque to 12 Nm (9 ft-lbs).
• Reconnect the coil electrical connector until it clicks.

Step 3: Remove the air duct and throttle body connections (to access rear bank)

• Use a 10mm socket to loosen the intake tube clamps and remove the air duct from the throttle body.
• Unplug the throttle body electrical connector; use a pick tool gently if needed.
• Disconnect any small vacuum/breather hoses from the intake tube using needle-nose pliers for spring clamps.

Step 4: Remove the upper intake manifold (rear bank access)

• Disconnect the electrical connectors and vacuum hoses attached to the upper intake manifold; label with painter’s tape and marker.
• Use a 12mm socket and ratchet to remove the upper intake manifold bolts/nuts.
• Lift the upper intake manifold straight up and out. If it’s stuck, gently rock it—do not pry hard on sealing surfaces.
• Immediately place clean rags into the exposed intake runners/ports to keep hardware and dirt out.
• Remove and discard the old upper intake manifold gaskets.
• Count tools/bolts before removing the rags.

Step 5: Replace the REAR bank spark plugs

• Unplug the rear ignition coil connectors.
• Use a 10mm socket to remove the coil bolts, then remove the coils.
• Blow out each spark plug well using compressed air blow gun.
• Use a 5/8" spark plug socket, extension set, and a universal joint to remove each rear spark plug.
• Install new plugs by hand first, then tighten with a torque wrench: Torque to 18 Nm (13 ft-lbs).
• Reinstall coils with a small dab of dielectric grease in each boot.
• Tighten coil bolts with a torque wrench: Torque to 12 Nm (9 ft-lbs), then reconnect the connectors.

Step 6: Reinstall the upper intake manifold with new gaskets

• Remove the rags from the intake ports.
• Install the new upper intake manifold gaskets in their grooves.
• Set the upper intake manifold back in place carefully (don’t pinch gaskets or trap wiring).
• Hand-start all bolts/nuts first, then tighten evenly with a 12mm socket.
• Tighten the upper intake manifold fasteners using a torque wrench: Torque to 25 Nm (18 ft-lbs).
• Reconnect all vacuum hoses and electrical connectors.

Step 7: Reassemble the intake tube and finish up

• Reinstall the intake tube and tighten clamps with a 10mm socket.
• If the throttle body was removed during your access, replace the gasket and torque the throttle body fasteners: Torque to 12 Nm (9 ft-lbs) using a 10mm socket.
• Reinstall the engine cover.
• Reconnect the negative battery cable using a 10mm socket.

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✅ After Repair

• Start the engine and let it idle. It may run slightly rough for a few seconds while the computer relearns.
• Listen for a hissing sound (vacuum leak) around the intake manifold area.
• Road test: light throttle first, then moderate acceleration. Verify no check engine light returns.
• If you disconnected the battery, perform an idle relearn: warm engine fully, turn all accessories off, and let it idle undisturbed for about 5 minutes.

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💰 DIY vs Shop Cost

Shop Cost: $450-$750 (parts + labor)

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

You Save: $230-$660 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2.5-4.5 hours.

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🎯 Ready to get started?

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