🔧 Cadenza - Spark Plug Replacement

On your Cadenza, you’ll replace all 6 spark plugs (one per cylinder) to restore strong ignition, smooth idle, and fuel economy. The front 3 plugs are easy to access; the rear 3 usually require removing the upper intake manifold to reach the ignition coils.

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

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⚠️ Safety & Precautions

• ⚠️ Work on a cold engine to avoid burns and prevent damaging aluminum threads.
• ⚠️ Disconnect the negative battery terminal to prevent accidental shorts.
• ⚠️ Keep dirt out of the engine: do not let anything fall into the intake ports.
• ⚠️ Do not over-tighten spark plugs; the cylinder heads are aluminum.
• ⚠️ Use only a small amount of dielectric grease; too much can cause misfires.

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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 (10-60 ft-lbs range)
• 5/8" spark plug socket
• 3/8" drive extension set (3", 6", 10")
• 3/8" drive swivel/universal joint
• Flathead screwdriver (medium)
• Needle-nose pliers
• Trim clip removal tool
• Compressed air blow gun
• Vacuum cleaner with crevice tool
• Shop towels
• Painter’s tape and marker
• Magnetic pickup tool

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Iridium spark plugs (correct fit for 3.3L) - 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.
• Let the engine cool fully (at least 1 hour after driving).
• Disconnect the negative battery cable using a 10mm socket.
• Use painter’s tape and marker to label any hoses/connectors you unplug, so they go back to the same place.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Assumption (best-effort): Rear-bank access requires upper intake manifold removal (common on transverse 3.3L V6).

Step 1: Remove the engine cover

• Pull up firmly on the plastic engine cover to pop it off the rubber grommets (use a trim clip removal tool if needed).
• Set the cover aside.

Step 2: Remove the front-bank ignition coils (front 3 cylinders)

• Unplug each coil electrical connector by pressing the tab and pulling back (use a flathead screwdriver gently if stuck).
• Remove the coil hold-down bolt with a 10mm socket.
• Twist the coil slightly and pull it straight up.
• Keep coils in order to avoid mix-ups.

Step 3: Clean the spark plug wells

• Blow out dirt around each spark plug hole using a compressed air blow gun.
• If needed, vacuum loose debris using a vacuum cleaner with crevice tool.
• This prevents dirt from falling into the cylinder when the plug comes out.

Step 4: Remove and replace the front-bank spark plugs

• Remove each plug using a 5/8" spark plug socket, 3/8" ratchet, and a 3/8" extension.
• Thread the new plug in by hand first using the spark plug socket and extension only (no ratchet) to avoid cross-threading.
• Tighten with a torque wrench (a tool that tightens to an exact value): Torque to 18-22 Nm (13-16 ft-lbs).
• If your new plugs come pre-gapped, do not bend the electrode; install as-is.

Step 5: Reinstall the front ignition coils

• Add a tiny smear of dielectric grease inside the tip of each coil boot (it helps prevent moisture and eases future removal).
• Push the coil straight down until it fully seats on the plug.
• Install the coil hold-down bolt with a 10mm socket; snug it (do not over-tighten).
• Reconnect the electrical connectors until they click.

Step 6: Remove the air ducting to access the upper intake area

• Loosen hose clamps using a flathead screwdriver.
• Remove any 10mm socket fasteners holding the duct/air tube.
• Lift the ducting out and set it aside.

Step 7: Remove the throttle body (as needed for intake removal)

• Unplug the throttle body connector by pressing the tab and pulling back.
• Remove the throttle body bolts using a 10mm socket.
• Remove and discard the old throttle body gasket (plan to install a new one).
• Place the throttle body aside on a clean towel (avoid stressing hoses/wiring).

Step 8: Remove the upper intake manifold (rear-bank access)

• Label and disconnect any vacuum hoses/PCV hoses using needle-nose pliers (for spring clamps) and your painter’s tape and marker.
• Unplug any intake-related connectors you need to move out of the way.
• Remove the upper intake manifold bolts using a 12mm socket, ratchet, and extensions.
• Lift the manifold off carefully.
• Immediately stuff each exposed intake port with a clean shop towel so nothing falls in.

Step 9: Replace the rear-bank spark plugs (rear 3 cylinders)

• Remove the rear ignition coils the same way as the front using a 10mm socket.
• Blow out each plug well using the compressed air blow gun.
• Remove and install plugs using a 5/8" spark plug socket, extensions, and a swivel/universal joint (a pivoting adapter that helps reach angled fasteners).
• Tighten new plugs with a torque wrench: Torque to 18-22 Nm (13-16 ft-lbs).
• Reinstall coils with a small amount of dielectric grease and reconnect the connectors.

Step 10: Reinstall the upper intake manifold with new gaskets

• Remove the shop towels from the intake ports (count them to confirm all are out).
• Remove old intake gaskets and install the new upper intake manifold gasket set.
• Set the manifold in place and start all bolts by hand.
• Tighten the manifold bolts evenly using a torque wrench: Torque to 18-22 Nm (13-16 ft-lbs).

Step 11: Reinstall throttle body and air ducting

• Install a new throttle body gasket.
• Reinstall throttle body bolts using a 10mm socket; tighten evenly (snug, do not strip).
• Reconnect the throttle body electrical connector.
• Reinstall intake ducting and tighten clamps using a flathead screwdriver.

Step 12: Reconnect battery and reinstall engine cover

• Reconnect the negative battery cable using a 10mm socket.
• Press the engine cover back onto its mounting grommets.

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✅ After Repair

• Start the engine and let it idle for 2-3 minutes.
• Listen for hissing (vacuum leak) and watch for a check engine light.
• Verify the idle is smooth and the throttle response feels normal.
• Take a short test drive, then recheck that all hose clamps and connectors are secure.

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💰 DIY vs Shop Cost

Shop Cost: $350-$700 (parts + labor)

DIY Cost: $80-$220 (parts only)

You Save: $270-$480 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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