🔧 Altima - Spark Plug Replacement

On your Altima 2.5L, the spark plugs sit under the ignition coils on top of the engine. Replacing them restores smooth starting, idle quality, and fuel economy, especially if you’re overdue on maintenance.

Difficulty Level: Beginner | Estimated Time: 1.0-2.0 hours

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⚠️ Safety & Precautions

• ⚠️ Let the engine cool fully (hot aluminum threads can strip).
• ⚠️ Work in a well-ventilated area and keep sparks/flames away.
• ⚠️ Disconnect the negative battery cable if you’re prone to bumping connectors (recommended for first-timers).
• ⚠️ Do not drop anything into the spark plug holes.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 3/8" ratchet
• 3/8" torque wrench
• 3/8" extension set
• 5/8" spark plug socket
• Flathead screwdriver
• Pick tool (small)
• Compressed air blower
• Feeler gauge (metric or inch)
• Dielectric grease applicator
• Clean shop towels
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Spark plugs (iridium/platinum, correct fit for 2.5L) - Qty: 4
• Dielectric grease - Qty: 1
• Ignition coil boot set (optional, if boots are torn or oil-soaked) - Qty: 1

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📋 Before You Begin

• Park on level ground and set the parking brake.
• Open the hood and let the engine cool completely.
• If disconnecting the battery: use a 10mm socket to remove the negative terminal and tuck it aside so it can’t spring back.
• Label coil connectors 1–4 if you want extra confidence.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover (if equipped)

• Remove any plastic cover fasteners using a 10mm socket or a flathead screwdriver (depending on what’s installed).
• Lift the cover off and set it aside.

Step 2: Unplug the ignition coil connectors

• Each spark plug has an ignition coil on top (the coil makes the spark).
• Press the connector lock tab and unplug each coil connector by hand.
• If a tab is stubborn, gently help it with a pick tool (small) (don’t pry hard).

Step 3: Remove the ignition coils

• Remove each coil hold-down bolt using a 10mm socket and 3/8" ratchet.
• Twist the coil slightly, then pull straight up to remove it.
• Set coils aside in order so they go back to the same cylinder.
• When reinstalling later: Torque to 7.5 Nm (66 in-lbs).

Step 4: Clean the spark plug wells

• Blow out dirt around each plug using a compressed air blower.
• This prevents debris from falling into the cylinder when the plug comes out.
• Hold a towel nearby to catch dust.

Step 5: Remove the old spark plugs

• Install a 5/8" spark plug socket on a 3/8" extension and 3/8" ratchet.
• Loosen each plug counterclockwise and remove it carefully.
• If a plug feels extremely tight, stop and work it gently back-and-forth to avoid thread damage.

Step 6: Check and prepare the new spark plugs

• Use a feeler gauge to confirm the gap matches spec: 1.1 mm (0.043 in).
• If the plugs are iridium, do not force-bend the tiny center tip; if the gap is off, exchange the plug.
• Do not use anti-seize unless the plug maker specifically requires it (most modern plugs are pre-coated).

Step 7: Install the new spark plugs

• Start each plug by hand using the spark plug socket and extension only (no ratchet at first).
• Thread it in until it seats smoothly. If it doesn’t, back out and try again (cross-threading is expensive).
• Tighten with a 3/8" torque wrench: Torque to 20 Nm (15 ft-lbs).

Step 8: Reinstall ignition coils and connectors

• Put a tiny smear of dielectric grease inside each coil boot (dielectric grease helps prevent moisture and makes future removal easier).
• Push each coil straight down until fully seated.
• Install the coil bolts using a 10mm socket, then Torque to 7.5 Nm (66 in-lbs) with a torque wrench.
• Reconnect each coil connector until it clicks.

Step 9: Reinstall engine cover and reconnect battery

• Reinstall the engine cover using a 10mm socket or flathead screwdriver.
• If disconnected, reconnect the negative battery terminal using a 10mm socket.

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✅ After Repair

• Start the engine and let it idle for 1–2 minutes. It should run smooth with no shaking.
• If the check engine light is on, read/clear codes with a scan tool (misfire codes are commonly P0300–P0304).
• Take a short test drive and recheck for any flashing check engine light (stop driving if it flashes).
• Keep the old plugs to compare cylinder condition.

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💰 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 1.0-1.5 hours.

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🎯 Ready to get started?

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