🔧 Impala - Spark Plug Replacement

Changing the spark plugs on your Impala restores strong ignition, smooth idle, and fuel economy—especially if you’re getting a rough run or a misfire. The key is to work one plug at a time so the plug wires don’t get mixed up.

Difficulty Level: Intermediate | Estimated Time: 1.5-3.0 hours

---

⚠️ Safety & Precautions

• ⚠️ Work on a fully cool engine to avoid burns and stripped threads.
• ⚠️ Disconnect the negative battery cable to prevent accidental arcing.
• ⚠️ Don’t pull spark plug wires by the wire—pull by the boot (the thick rubber end).
• ⚠️ Keep dirt out of the plug holes; debris can damage the engine.

---

🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Mechanic gloves
• Flashlight
• Fender cover
• 10mm socket
• 3/8" drive ratchet
• 3/8" drive extension set (6" and 12")
• 3/8" drive universal joint swivel
• 5/8" spark plug socket (rubber insert)
• Torque wrench (ft-lb)
• Spark plug gap gauge
• Compressed air blow gun
• Flat trim tool
• Dielectric grease applicator (cotton swab)

---

🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (correct fit for your Impala 3.5L) - Qty: 6
• Dielectric grease - Qty: 1
• Spark plug wire set - Qty: 1 Optional, but smart if old

---

📋 Before You Begin

• 🧰 Park on level ground, set the parking brake, and open the hood.
• 🧰 Let the engine cool completely (at least 1 hour after driving).
• 🧰 Use a 10mm socket to disconnect the negative battery cable and move it aside.
• 🧰 If you’re replacing plug wires, plan to do one wire at a time so routing stays correct.

---

🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover (if equipped)

• Use a 10mm socket to remove the engine cover fasteners (if present).
• Lift the cover off and set it aside.

Step 2: Locate the spark plug wires and pick a starting cylinder

• Find the spark plug wires going to the front and rear cylinder banks.
• Pick one easy plug to start with (usually a front bank plug).
• Do one plug start-to-finish.

Step 3: Remove one spark plug wire

• Grab the boot (thick rubber end) and twist it slightly to break it loose.
• Pull the boot straight off the spark plug.
• If it’s stuck, use a flat trim tool gently under the boot to help lift—don’t tear the boot.
• Apply a tiny dab of dielectric grease inside the boot using the dielectric grease applicator (cotton swab). (Dielectric grease helps prevent moisture and makes future removal easier.)

Step 4: Clean around the spark plug

• Use a compressed air blow gun to blow dirt away from the plug hole before removing the plug.
• This helps prevent grit from falling into the cylinder.

Step 5: Remove the spark plug

• Install the 5/8" spark plug socket (rubber insert) on a 3/8" drive extension (6" or 12") and 3/8" drive ratchet.
• For tight angles, add the 3/8" drive universal joint swivel.
• Turn counterclockwise to remove the spark plug, then lift it out with the socket.

Step 6: Check and set the gap on the new plug

• Use a spark plug gap gauge to verify the gap matches the under-hood emissions label specification.
• If the plug is “pre-gapped,” still verify it—shipping can bend the electrode.

Step 7: Install the new spark plug (start by hand)

• Place the new plug into the 5/8" spark plug socket (rubber insert).
• Use the 3/8" drive extension only (no ratchet) to thread the plug in by hand several turns.
• If it doesn’t spin in easily, back it out and try again to avoid cross-threading.

Step 8: Torque the spark plug

• Set your torque wrench (ft-lb) and tighten the plug to Torque to 15 ft-lbs (20 Nm).
• Don’t over-tighten—aluminum threads strip.

Step 9: Reinstall the spark plug wire

• Push the boot onto the plug until you feel/notice it fully seat.
• Route the wire the same way it was originally (use factory clips/holders).

Step 10: Repeat for the remaining 5 spark plugs

• Repeat Steps 3–9 for each plug, always working one cylinder at a time.
• For rear bank plugs, use the 3/8" drive universal joint swivel and 12" extension to reach from above.

Step 11: Reinstall the engine cover and reconnect the battery

• Reinstall the engine cover using a 10mm socket (snug, do not over-tighten).
• Reconnect the negative battery cable using a 10mm socket.

---

✅ After Repair

• ✅ Start the engine and let it idle for 1–2 minutes. It should run smooth.
• ✅ Listen for a ticking sound (can indicate a loose plug) and recheck any suspect cylinder.
• ✅ If the check engine light is on or flashing, stop and re-check wire seating and routing.
• ✅ Take a short test drive and verify there’s no hesitation under light acceleration.

---

💰 DIY vs Shop Cost

Shop Cost: $250-$450 (parts + labor)

DIY Cost: $40-$120 (parts only)

You Save: $130-$410 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.5-3.0 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.