🔧 GX460 - Spark Plug Replacement

On your GX460, replacing the spark plugs restores strong ignition, smooth idle, and fuel economy. You’ll remove the ignition coils, swap the plugs, and reinstall everything with correct torque so you don’t damage aluminum cylinder head threads.

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

---

⚠️ Safety & Precautions

• ⚠️ Work on a fully cool engine to avoid burns and prevent thread damage.
• ⚠️ Keep dirt out of plug holes; debris can damage the engine.
• ⚠️ Do not over-tighten spark plugs in the aluminum heads.
• ⚠️ Battery disconnect is recommended: remove negative terminal to prevent accidental shorts.
• ⚠️ Assumption: rear-bank access may be tight; steps include optional intake removal if needed.

---

🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• 10mm socket
• 12mm socket
• 14mm socket
• 3/8" ratchet
• 3/8" torque wrench (10-30 ft-lb range)
• 6" extension (3/8")
• 12" extension (3/8")
• 3/8" universal joint swivel
• 5/8" spark plug socket (rubber insert or магнит insert)
• Flathead screwdriver
• Trim clip removal tool
• Needle-nose pliers
• Flashlight
• Compressed air blow gun
• Shop vacuum
• Clean shop rags
• Magnetic pickup tool

---

🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (OEM-spec iridium) - Qty: 8
• Dielectric grease - Qty: 1
• Upper intake manifold gasket set - Qty: 1
• Throttle body gasket - 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).
• Disconnect the battery negative terminal using a 10mm socket.
• Tip: A torque wrench measures tightening force so you don’t strip threads.
• Tip: A spark plug socket grips the plug so it won’t fall into the well.

---

🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Lift off the plastic engine cover (it pulls up on most GX460 covers); use a trim clip removal tool if clips resist.
• Set it aside where it won’t get stepped on.

Step 2: Remove the air intake tube (to create working room)

• Loosen the intake hose clamps using a flathead screwdriver.
• Disconnect any small hoses/clips carefully using needle-nose pliers.
• Remove the intake tube and set it aside with a clean shop rag covering the throttle opening area to block dirt.

Step 3: Unplug and remove the ignition coils (one cylinder at a time)

• Pick one coil to start so parts don’t get mixed up.
• Press the electrical connector tab and unplug it (use a flathead screwdriver gently if needed).
• Remove the coil hold-down bolt with a 10mm socket.
• Twist the coil slightly and pull it straight up and out.
• Do one coil and plug at a time.

Step 4: Clean the spark plug well

• Blow out the plug tube using compressed air blow gun while holding a shop vacuum nearby.
• This prevents debris from falling into the cylinder when the plug comes out.

Step 5: Remove the old spark plug

• Install a 5/8" spark plug socket (rubber insert or магнит insert) on a 12" extension (3/8") and 3/8" ratchet.
• For tight cylinders (especially near the firewall), add a 3/8" universal joint swivel as needed.
• Turn counterclockwise to remove the plug, then lift it out carefully.
• If it feels stuck, stop and work it back-and-forth gently to avoid thread damage.

Step 6: Install the new spark plug

• Confirm the new plug matches the old plug in length and seat style.
• Carefully start the new plug by hand using the 5/8" spark plug socket and extension only (no ratchet yet).
• Thread it in smoothly; if it binds, back it out and restart to avoid cross-threading.
• Tighten using a 3/8" torque wrench (10-30 ft-lb range): Torque to 18 Nm (13 ft-lbs).
• Do not apply anti-seize unless your plug maker specifically requires it; most OEM-style iridium plugs are plated.

Step 7: Reinstall the ignition coil

• Apply a small dab of dielectric grease inside the rubber boot (helps moisture sealing).
• Push the coil down until it fully seats on the plug.
• Install the coil bolt with a 10mm socket, then tighten with a 3/8" torque wrench: Torque to 10 Nm (89 in-lbs).
• Reconnect the coil electrical connector until it clicks.

Step 8: Repeat for all 8 cylinders

• Repeat Steps 3-7 for each remaining cylinder.
• Use the flashlight often to confirm connectors are fully seated and no harnesses are pinched.

Step 9 (If needed): Optional rear-bank access help

• If you cannot physically reach the rear plugs, remove additional top-side components for space.
• Remove the throttle body fasteners using a 10mm socket; replace the gasket during reassembly.
• If removing the upper intake manifold, remove fasteners with a 12mm socket and replace the manifold gaskets.
• Reinstall and tighten evenly: Upper intake manifold fasteners torque to 21 Nm (15 ft-lbs).
• Reinstall throttle body: Torque to 10 Nm (89 in-lbs).
• Keep bolts organized by location.

Step 10: Reinstall the air intake tube and engine cover

• Reinstall the intake tube and tighten clamps using a flathead screwdriver.
• Reconnect any hoses/clips using needle-nose pliers.
• Reinstall the engine cover by pressing it into place.
• Reconnect the battery negative terminal using a 10mm socket.

---

✅ After Repair

• Start the engine and let it idle for 1-2 minutes.
• Listen for misfires (shaking) and check that the idle is smooth.
• Make sure there are no warning lights; if a check engine light appears, recheck coil connectors.
• Do a short test drive, then recheck for any loose intake clamps or hissing (vacuum leak sound).

---

💰 DIY vs Shop Cost

Shop Cost: $450-$900 (parts + labor)

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

You Save: $360-$680 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.

---

🎯 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.