🔧 Ridgeline - Spark Plug Replacement

On your Ridgeline, the front 3 spark plugs are easy to access, but the rear 3 sit under the upper intake manifold (the top half of the intake). Replacing all 6 restores smooth idle, power, and fuel economy, and helps prevent misfires as mileage builds.

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

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⚠️ Safety & Precautions

• ⚠️ Work on a cold engine to avoid burns and stripped plug threads.
• ⚠️ Disconnect the negative battery cable to prevent accidental short circuits.
• ⚠️ Keep dirt out of the intake ports—cover openings with clean shop towels.
• ⚠️ Do not mix up ignition coil connectors; label them if needed.
• ⚠️ Avoid dropping anything into the intake manifold runners.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• Floor jack (rated 3-ton minimum)
• Jack stands (rated 3-ton minimum)
• Wheel chocks
• 3/8" drive ratchet
• 3/8" drive torque wrench (10-80 ft-lbs range)
• 3/8" drive extension set (3", 6", 10")
• 3/8" drive wobble extension
• 14mm thin-wall spark plug socket (3/8" drive)
• 10mm socket (3/8" drive)
• 12mm socket (3/8" drive)
• 10mm wrench
• Flat-blade screwdriver
• Needle-nose pliers
• Trim clip removal tool
• Pick tool
• Small flashlight
• Shop towels
• Compressed air blow gun
• Magnetic pickup tool

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (iridium, OEM-style) - 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 wrench to disconnect the negative battery cable and move it aside so it can’t spring back.
• Lay out 6 new plugs and keep them clean—don’t drop them.
• Take a quick photo of hoses before removal.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover and air intake duct

• Remove the engine cover (if equipped) by pulling it upward by hand.
• Use a flat-blade screwdriver to loosen the intake duct hose clamps.
• Unclip/remove any intake snorkel clips using a trim clip removal tool.
• Disconnect the air duct and move it out of the way.

Step 2: Replace the front bank spark plugs (front 3 cylinders)

• Unplug one ignition coil at a time by pressing the connector tab (use a pick tool gently if the tab is stubborn).
• Remove the coil hold-down bolt using a 10mm socket.
• Pull the coil straight up and out.
• Blow out the spark plug well using compressed air blow gun so dirt can’t fall into the cylinder.
• Remove the spark plug using a 14mm thin-wall spark plug socket, 3/8" drive ratchet, and a 3/8" drive extension.
• Install the new spark plug by hand first using the socket/extension (no ratchet) to avoid cross-threading.
• Tighten the spark plug with a 3/8" drive torque wrench: Torque to 18 N·m (13 ft-lbs).
• Add a small smear of dielectric grease inside the coil boot, then reinstall the coil.
• Tighten the coil bolt with a 3/8" drive torque wrench: Torque to 12 N·m (9 ft-lbs).
• Reconnect the coil electrical connector and repeat for the other two front cylinders.
• Do not use anti-seize on Honda plugs.

Step 3: Remove components on the upper intake manifold

• Disconnect the throttle body electrical connector(s) using your fingers and a pick tool only if needed.
• Disconnect vacuum/EVAP hoses from the upper intake, using needle-nose pliers where spring clamps are used.
• Unbolt the throttle body from the upper intake using a 10mm socket and carefully set it aside (don’t kink hoses).
• Cover the throttle opening with a shop towel to keep debris out.

Step 4: Remove the upper intake manifold (to access the rear 3 plugs)

• Remove the upper intake manifold mounting bolts/nuts using a 12mm socket.
• Lift the upper intake manifold straight up and off. Use a small flashlight to confirm nothing is still connected.
• Immediately place shop towels into the lower intake ports so nothing can fall in.
• Remove and discard the old upper intake manifold gaskets using a pick tool.

Step 5: Replace the rear bank spark plugs (rear 3 cylinders)

• Unplug one rear ignition coil connector at a time.
• Remove the coil hold-down bolt using a 10mm socket, then pull the coil out.
• Blow out the spark plug wells using the compressed air blow gun.
• Remove each spark plug using a 14mm thin-wall spark plug socket, 3/8" drive ratchet, and 3/8" drive wobble extension as needed for clearance.
• Install new plugs by hand first, then torque with a 3/8" drive torque wrench: Torque to 18 N·m (13 ft-lbs).
• Apply a small smear of dielectric grease inside each coil boot, reinstall coils, and torque coil bolts: Torque to 12 N·m (9 ft-lbs).

Step 6: Reinstall the upper intake manifold with new gaskets

• Remove the shop towels from the intake ports.
• Install the new upper intake manifold gaskets (make sure they sit flat in their grooves).
• Set the upper intake manifold back in place.
• Install bolts/nuts finger-tight first, then tighten evenly using a 12mm socket.
• Final tighten using a 3/8" drive torque wrench: Torque to 22 N·m (16 ft-lbs).
• Tighten in a crisscross pattern.

Step 7: Reinstall the throttle body and intake ducting

• Install a new throttle body gasket.
• Reinstall the throttle body fasteners using a 10mm socket, then torque: Torque to 22 N·m (16 ft-lbs).
• Reconnect any electrical connectors and hoses you removed.
• Reinstall the air intake duct and tighten clamps using a flat-blade screwdriver.
• Reinstall the engine cover by pressing it into place.

Step 8: Reconnect the battery

• Reconnect the negative battery cable using a 10mm wrench and tighten snugly.
• Verify no tools or towels are left in the engine bay.

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✅ After Repair

• Start your Ridgeline and let it idle for 2–3 minutes.
• Expect a brief idle fluctuation after battery disconnect; it should settle.
• Check for air leaks (hissing), a check engine light, or a rough idle (often a missed hose/connector).
• Take a 10-minute test drive and recheck that everything feels smooth under light acceleration.

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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 2.5-4.5 hours.

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🎯 Ready to get started?

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