🔧 Altima - Spark Plug Replacement

On your Altima, the spark plugs sit under the ignition coils on top of the engine. Replacing them restores smooth starting, idle, and fuel economy, and helps prevent misfires.

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

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⚠️ Safety & Precautions

• ⚠️ Work on a fully cool engine to avoid burns and damaged threads.
• ⚠️ Keep dirt out of the plug holes; debris can fall into the cylinder.
• ⚠️ If you disconnect the battery, use a 10mm wrench and remove the negative terminal first.
• ⚠️ Do not over-tighten spark plugs; the cylinder head is aluminum.

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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 Nm range)
• 10mm socket
• 5/8" (16mm) spark plug socket
• 3/8" drive extension set (3" and 6")
• Flathead screwdriver
• Compressed air blow gun
• Shop vacuum
• Trim clip tool
• 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 Altima 2.5L) - Qty: 4
• Dielectric grease (small tube) - Qty: 1

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📋 Before You Begin

• Park on level ground, engine off, and let the engine cool completely.
• Open the hood and remove any loose items around the engine.
• Tip: Take a quick photo before unplugging anything.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover (if equipped)

• Remove any plastic fasteners using a trim clip tool.
• Lift the cover off. If it’s held by bolts, remove them with a 10mm socket.

Step 2: Unplug and remove the ignition coils

• There are 4 ignition coils on top of the engine—one per spark plug.
• Press the locking tab and unplug each coil connector. If the tab is stubborn, gently help it with a flathead screwdriver.
• Remove each coil hold-down bolt using a 10mm socket.
• Pull the coil straight up to remove it. Tip: Wiggle gently—don’t yank the wiring.
• When reinstalling later: Torque to 8 Nm (71 in-lb) on each coil bolt.

Step 3: Clean around the spark plug tubes

• Use a shop vacuum to remove loose dirt around each plug hole.
• Blow out the plug tubes using compressed air blow gun while wearing safety glasses.
• Tip: This prevents grit from falling into the engine.

Step 4: Remove the old spark plugs

• Install a 5/8" (16mm) spark plug socket on a 3/8" drive extension and 3/8" drive ratchet.
• Loosen and remove each spark plug, one at a time.
• If one feels extremely tight, stop and work it slowly to avoid thread damage.

Step 5: Install the new spark plugs (start by hand)

• Do not add anti-seize unless the plug manufacturer specifically instructs it.
• Place a new plug into the spark plug socket and carefully lower it into the tube.
• Thread it in by hand first using only the extension (no ratchet) so you can “feel” the threads start correctly.
• If it doesn’t turn easily by hand, back it out and start again (this avoids cross-threading).
• Tighten using a 3/8" drive torque wrench: Torque to 18 Nm (13 ft-lb).

Step 6: Reinstall the ignition coils

• Put a tiny dab of dielectric grease inside each coil boot. (Dielectric grease is a non-conductive grease that helps prevent moisture and makes boots easier to remove later.)
• Push each coil straight down onto its spark plug until it seats.
• Install coil bolts using a 10mm socket, then finish with a torque wrench: Torque to 8 Nm (71 in-lb).
• Plug the electrical connectors back in until they click.

Step 7: Reinstall the engine cover

• Reinstall the cover and fasteners using a 10mm socket or trim clip tool (as equipped).

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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 engine runs rough, shut it off and re-check that every coil connector is fully clicked in.
• Take a short test drive and confirm no hesitation on acceleration.

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💰 DIY vs Shop Cost

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

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

You Save: $210-$330 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.0-2.0 hours.

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🎯 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.