🔧 K900 - Spark Plug Replacement

Replacing the spark plugs restores strong ignition, smooth idle, and fuel economy—especially if you’re near the scheduled plug interval or have a misfire. On your K900’s 3.8L V6, the front bank is easy, and the rear bank is tighter and may require removing the upper intake manifold for access.

Assumption: Your K900 has the 3.8L V6 with coil-on-plug ignition; rear plugs may require upper intake manifold removal for clearance.

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

---

⚠️ Safety & Precautions

• ⚠️ Work on a fully cool engine to avoid burns and to prevent thread damage in the cylinder head.
• ⚠️ Disconnect the negative battery terminal if you’ll unplug many sensors (helps prevent accidental shorts and check-engine lights).
• ⚠️ Keep dirt out of the engine—blow debris away from the plug wells before removing plugs.
• ⚠️ Do not over-tighten spark plugs; the cylinder head is aluminum and threads can strip.

---

🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• 10mm socket
• 12mm socket
• 14mm socket
• 3/8" drive ratchet
• 3/8" drive torque wrench (10–50 ft-lbs range)
• 3/8" drive extensions (3", 6", 12")
• 3/8" drive universal joint
• 5/8" spark plug socket
• Flathead screwdriver
• Needle-nose pliers
• Trim clip tool
• Compressed air blow gun
• Feeler gauge set
• Magnetic pickup tool
• Shop light

---

🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (iridium, correct heat range for K900 3.8L) - Qty: 6
• Upper intake manifold gasket set - Qty: 1
• Throttle body gasket - Qty: 1
• Dielectric grease - Qty: 1

---

📋 Before You Begin

• Park on level ground, shift to Park, and set the parking brake.
• Let the engine cool completely (at least 1–2 hours after driving).
• Open the hood and remove the negative battery cable using a 10mm socket and 3/8" drive ratchet.
• Set up your tools and keep bolts grouped by area (front bank vs rear bank) so nothing gets mixed up.

---

🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Lift the plastic engine cover straight up to release the rubber grommets (no tools on most covers).
• If any trim clips are present, remove them with a trim clip tool.

Step 2: Remove the air intake ducting (for working room)

• Loosen the intake hose clamp(s) using a flathead screwdriver.
• Unclip/remove the ducting and set it aside.

Step 3: Replace spark plugs on the front bank (radiator-side)

• Unplug each ignition coil connector (press the lock tab, then pull). Use needle-nose pliers only gently if a tab is stubborn.
• Remove the coil hold-down bolt using a 10mm socket and 3/8" drive ratchet.
• Pull the coil straight up and out. Twist slightly to break the seal.
• Blow out the spark plug well using a compressed air blow gun so debris can’t fall into the cylinder.
• Remove the spark plug using a 5/8" spark plug socket, 3/8" drive ratchet, and the needed 3/8" drive extensions.
• Check the new plug gap using a feeler gauge set (do not pry hard on iridium tips). Install only if gap matches the plug maker’s spec for your K900.
• Thread the new spark plug in by hand using the 5/8" spark plug socket and a 3/8" drive extension (no ratchet at first) to avoid cross-threading.
• Tighten with a 3/8" drive torque wrench: Torque to 18–22 Nm (13–16 ft-lbs).
• Apply a small amount of dielectric grease inside the coil boot (it helps prevent moisture and makes future removal easier).
• Reinstall the coil and coil bolt using a 10mm socket, then Torque to 8–10 Nm (6–7 ft-lbs).
• Reconnect the coil connector.

Step 4: Gain access to the rear bank (firewall-side)

• If you can clearly reach the rear coils/plugs with a 3/8" drive universal joint and 3/8" drive extensions, you may skip intake removal and proceed carefully.
• If access is tight (common), remove the upper intake manifold:
• Remove any vacuum hoses/PCV hoses using needle-nose pliers and gently twist hoses free by hand.
• Unplug intake/throttle body related connectors by hand (press the lock tab; pull straight).
• Remove the throttle body fasteners using a 10mm socket and 3/8" drive ratchet, then set the throttle body aside carefully.
• Remove the upper intake manifold bolts using a 12mm socket and 3/8" drive ratchet.
• Lift the upper intake manifold off and cover the intake ports with a clean rag immediately. Do not drop anything inside.

Step 5: Replace spark plugs on the rear bank (firewall-side)

• Unplug coil connectors by hand.
• Remove coil hold-down bolts using a 10mm socket.
• Pull coils straight up and out.
• Blow out plug wells using a compressed air blow gun.
• Remove each plug with a 5/8" spark plug socket, 3/8" drive ratchet, 3/8" drive extensions, and 3/8" drive universal joint.
• Install new plugs by hand first, then torque with a 3/8" drive torque wrench: Torque to 18–22 Nm (13–16 ft-lbs).
• Apply a small amount of dielectric grease in each coil boot, reinstall coils, and torque coil bolts: Torque to 8–10 Nm (6–7 ft-lbs).
• Reconnect coil connectors.

Step 6: Reinstall the upper intake manifold and throttle body (if removed)

• Remove the rags covering the intake ports.
• Install new upper intake manifold gasket set onto the manifold (do not reuse flattened gaskets).
• Set the manifold in place and start all bolts by hand.
• Tighten manifold bolts evenly in a crisscross pattern using a 12mm socket and 3/8" drive ratchet, then torque: Torque to 18–22 Nm (13–16 ft-lbs).
• Install a new throttle body gasket, reinstall the throttle body using a 10mm socket, then torque: Torque to 8–10 Nm (6–7 ft-lbs).
• Reconnect all vacuum hoses and electrical connectors (double-check each one clicks into place).

Step 7: Reinstall the intake ducting and engine cover

• Reinstall the air ducting and tighten clamps with a flathead screwdriver.
• Reinstall the engine cover by pressing it down into the grommets.
• Reconnect the negative battery cable using a 10mm socket.

---

✅ After Repair

• Start the engine and let it idle for 2–3 minutes. A slightly rough idle for a few seconds can be normal if the intake was removed.
• Listen for vacuum leaks (hissing) around the intake manifold and throttle body area.
• If the check-engine light comes on, re-check coil connectors and any intake/throttle connectors that may be unplugged.
• Take a short test drive, then re-check for any odd noises and confirm smooth acceleration.

---

💰 DIY vs Shop Cost

Shop Cost: $350-$750 (parts + labor)

DIY Cost: $70-$220 (parts only)

You Save: $280-$530 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.

---

🎯 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.