🔧 Altima - Spark Plug Replacement

You’ll be replacing the spark plugs in your Altima to keep the engine running smoothly, improve fuel economy, and prevent misfires. On your 2.5L engine, the plugs are under the plastic engine cover and coil packs on top of the engine.

Difficulty Level: Beginner | Estimated Time: 1–1.5 hours

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⚠️ Safety & Precautions

• 🔸 Let the engine cool completely before starting; hot parts can burn you.
• 🔸 Work in a well-ventilated area and keep the car in Park with the parking brake on.
• 🔸 Do not pull on ignition coil wires; always grab connectors by the plastic housing.
• 🔸 Avoid dropping anything into the spark plug holes; that can damage the engine.
• 🔸 Battery disconnect is not strictly required, but disconnecting the negative terminal adds safety if you’re nervous around wiring.

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🔧 Required Tools

You'll need the following tools for this repair:

• 🔸3/8" drive ratchet
• 🔸3/8" drive torque wrench (5–60 ft-lbs range)
• 🔸10mm socket
• 🔸5/8" spark plug socket (with rubber insert or magnet)
• 🔸3/8" drive extension (6" length)
• 🔸Flathead screwdriver (small)
• 🔸Needle-nose pliers
• 🔸Spark plug gap gauge (coin or wire style)
• 🔸Shop rag or clean cloth
• 🔸Dielectric grease
• 🔸Anti-seize compound (sparingly, optional if plugs are not pre-coated)
• 🔸Gloves
• 🔸Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• 🔸Iridium spark plugs (correct for 2.5L Altima) - Qty: 4
• 🔸Dielectric grease packet - Qty: 1
• 🔸Anti-seize compound - Qty: 1
• 🔸Throttle body/intake cleaner - Qty: 1 (optional for light cleaning around area)
• 🔸Shop towels - Qty: 1 pack

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📋 Before You Begin

• Park your Altima on level ground, shift to Park, and set the parking brake.
• Turn the engine off and remove the key; let the engine cool at least 30–45 minutes.
• If you want extra safety, disconnect the negative battery cable using a 10mm socket.
• Lay out your new spark plugs in order and keep them clean; do not touch the tips.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Open the hood using the interior hood release, then lift the hood and set the prop rod.
• The plastic engine cover on your Altima usually pulls up; grasp it with both hands and gently pull upward at the corners.
• If there are bolts holding it, use a 10mm socket and ratchet to remove them, then lift the cover off and set it aside.

Step 2: Identify ignition coils and work area

• You will see four black ignition coils sitting on top of the engine, each with an electrical connector; each coil sits over one spark plug.
• Blow or wipe away any loose dirt from the top of the engine using a shop rag to avoid debris falling into the plug holes.
• Do one cylinder at a time to avoid mixing parts.

Step 3: Disconnect the ignition coil connector (Cylinder 1)

• Pick one coil at the front; press the small plastic tab on the connector with your finger or a flathead screwdriver and gently pull the connector straight off.
• If it feels stuck, wiggle gently by the plastic housing, not the wires; you can use needle-nose pliers on the plastic if needed.

Step 4: Remove the ignition coil

• Use a 10mm socket and ratchet to remove the bolt holding the coil to the valve cover.
• Pull the coil straight up by hand; it may feel snug due to the rubber boot sealing to the spark plug.
• Set the coil aside in a clean area; do not rest the rubber boot on dirty surfaces.

Step 5: Remove the old spark plug

• Install the 5/8" spark plug socket onto a 3/8" drive extension and then onto your ratchet.
• Lower the socket straight down into the spark plug well until it seats on the plug.
• Turn the ratchet counterclockwise to loosen the plug completely.
• Once loose, spin the extension by hand and lift the plug out; the rubber insert or magnet in the spark plug socket should hold it.
• If it feels cross-threaded or extremely tight, stop and back it out gently, do not force it.

Step 6: Check and prepare the new spark plug

• Remove a new plug from its box and keep the tip away from dirt.
• Use a spark plug gap gauge to quickly check the gap; Nissan spec is about 1.0–1.1 mm (0.039–0.043 in).
• Most iridium plugs for your Altima come pre-gapped; do not bend the center electrode. Only adjust very gently if the side electrode is obviously bent.
• If the plug threads are not pre-coated, apply a very thin smear of anti-seize compound to the threads only, avoiding the tip. Many modern plugs say “no anti-seize”; follow that note if present.

Step 7: Install the new spark plug

• Place the new plug into the 5/8" spark plug socket and extension, keeping it straight.
• Lower it carefully into the spark plug well and gently start turning the extension by hand clockwise to thread it in.
• It should turn easily by hand; if you feel resistance or cross-threading, back it out and try again.
• Once snug by hand, attach the ratchet and lightly tighten.
• Then use a torque wrench (3/8" drive) set to 18–22 Nm (13–16 ft-lbs) and tighten the plug until it clicks.
• Never overtighten; that can damage the cylinder head.

Step 8: Reinstall the ignition coil

• Put a small dab of dielectric grease inside the rubber boot of the coil (the end that goes over the spark plug). This helps sealing and future removal.
• Slide the coil straight down onto the plug until it seats fully.
• Install the coil retaining bolt with a 10mm socket and ratchet and snug it down; then torque to about 7–9 Nm (62–80 in-lbs).

Step 9: Reconnect the ignition coil connector

• Push the electrical connector back onto the coil until you hear or feel a click.
• Lightly tug on the connector to confirm it is locked in place.

Step 10: Repeat for the remaining cylinders

• Repeat Steps 3–9 for each of the remaining three coils and plugs, one at a time.
• Always fully finish one cylinder before moving to the next to avoid mixing parts or connectors.

Step 11: Reinstall the engine cover

• Place the engine cover back over the engine, lining up the mounting points.
• If it’s a push-on cover, press down firmly at each corner until it snaps in.
• If it uses bolts, reinstall them with a 10mm socket and ratchet and snug them by hand (no need for high torque).

Step 12: Reconnect the battery (if disconnected)

• If you removed the negative battery cable, reinstall it onto the terminal.
• Use a 10mm socket to tighten the clamp until secure, but do not over-tighten.

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✅ After Repair

• Start your Altima and let it idle; it should run smoothly without misfires or shaking.
• Watch for any warning lights on the dash; if a check engine light appears, recheck all coil connectors.
• Take a short test drive, listening for abnormal engine sounds or hesitation under acceleration.
• After your drive, recheck under the hood to ensure nothing is loose and the engine cover is secure.

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💰 DIY vs Shop Cost

Shop Cost: $220–$350 (parts + labor)

DIY Cost: $50–$120 (parts only)

You Save: $100–$250 by doing it yourself!

Shop labor rates vary but typically run $100–$150/hour. This repair takes a shop approximately 0.8–1.0 hours.

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