🔧 Altima - Spark Plug Replacement

This is a manageable job if you work on a completely cold engine and start every plug by hand. Your Altima uses four long-life iridium spark plugs, and Nissan specifies replacement every 105,000 miles. nissanusa.com)

Difficulty Level: Intermediate | Estimated Time: 1-2 hours

Verified specification: The KR20DDET uses four NGK DILKAR7N9HG-type plugs with a nominal 0.9 mm (0.035 inch) gap. Nissan says not to clean or regap these iridium plugs. carmanualsonline.info)

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⚠️ Safety & Precautions

• ⚠️ Let the engine become completely cold before removing the plugs.
• ⚠️ Switch the ignition off, engage the parking brake, and keep the key away from the vehicle.
• ⚠️ Never remove a plug while dirt is sitting around its well.
• ⚠️ Start each new plug by hand. Cross-threading can damage the aluminum cylinder head.
• ⚠️ Don’t use anti-seize compound unless the plug manufacturer specifically requires it.
• ⚠️ Don’t pry against the ignition coils or pull them by their wiring.
• ⚠️ Battery disconnection isn’t normally required for this repair.

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🔧 Required Tools

You'll need the following tools for this repair:

• 8mm socket
• 10mm socket
• 14mm thin-wall spark plug socket
• 3/8-inch drive ratchet
• 3/8-inch drive 6-inch extension
• 3/8-inch drive inch-pound torque wrench
• Small flat-blade screwdriver
• Compressed-air blow gun
• 0.9mm wire spark plug gap gauge
• Clean shop towels
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• KR20DDET-compatible iridium spark plugs - Qty: 4

Replace all four together. The spark-plug aisle is open in the parts sidebar and already scoped to your Altima.

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📋 Before You Begin

• Park on level ground, select Park, and engage the parking brake.
• Allow the engine to cool for several hours. Overnight is ideal.
• Open the hood and remove loose dirt from the top of the engine.
• Take a photo of any hoses or brackets before moving them.
• Work on one cylinder at a time so every coil returns to its original position.
• No infotainment service mode, scan tool, battery registration, or programming is required.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the engine cover

• Use the appropriate 8mm or 10mm socket if retaining fasteners are fitted.
• If the cover uses rubber grommets, grip it near each mounting point and pull straight upward.
• Set the cover and its fasteners aside.

Step 2: Clear access to the ignition coils

• Identify the four ignition coils positioned in a row on top of the engine.
• Use the 8mm or 10mm socket to move any small bracket obstructing direct access.
• Don’t disconnect intake hoses unless they genuinely block coil removal.

Step 3: Disconnect the first ignition coil

• Press the electrical connector lock and pull the connector straight backward.
• Use the small flat-blade screwdriver only to release a stubborn locking tab.
• Don’t pull on the wires. Connector repairs turn a simple tune-up into a bad afternoon.

Step 4: Remove the ignition coil

• Use the correctly fitting 8mm or 10mm socket and ratchet to remove the coil retaining bolt.
• Twist the coil gently to release its rubber boot, then pull it straight upward.
• Inspect the boot for cracks, swelling, oil, or white tracking marks.

Step 5: Clean the spark plug well

• Put on the safety glasses.
• Use the compressed-air blow gun to remove sand and debris from the well.
• Cover nearby openings with clean shop towels while blowing.
• If oil is pooled around the plug, stop and address the sealing leak before continuing.

Step 6: Remove the old spark plug

• Fit the 14mm thin-wall spark plug socket to the 6-inch extension and ratchet.
• Seat the socket fully and turn counterclockwise with steady pressure.
• Once loose, remove the ratchet and spin the plug out gently with the extension.
• If the plug becomes unusually tight, reverse direction slightly and work slowly. Don’t force it.

Step 7: Inspect the removed plug

• Check for heavy black carbon, wet fuel, oily deposits, a cracked insulator, or a damaged electrode.
• Compare all four old plugs as they come out. One noticeably different plug may identify a cylinder-specific problem.
• Keep the old plugs arranged in cylinder order until the engine has passed its final test.

Step 8: Inspect the new spark plug

• Confirm the new plug matches the old plug’s thread length and terminal arrangement.
• Use the 0.9mm wire spark plug gap gauge only to verify the nominal 0.9 mm (0.035 inch) gap.
• Don’t force a wedge-style gauge between the fine electrodes and don’t bend the electrode to adjust it. Nissan specifically warns against regapping its iridium plugs. nissanusa.com)
• Keep the plug threads clean and dry.

Step 9: Hand-thread the new spark plug

• Place the plug in the 14mm thin-wall spark plug socket and attach only the extension.
• Lower it carefully into the well so the electrode doesn’t strike the cylinder head.
• Turn the extension clockwise by hand for several complete rotations.
• If it doesn’t turn easily, remove it and start again. Never use the ratchet to begin the threads.

Step 10: Torque the spark plug

• Attach the inch-pound torque wrench to the extension and spark plug socket.
• Tighten the plug to 19.6 Nm (14 ft-lbs or 168 in-lbs). This specification is listed for the KR20DDET engine. lemon-manuals.gy
• Stop as soon as the torque wrench clicks. Don’t give it an extra pull.

Step 11: Reinstall the ignition coil

• Push the coil straight over the plug until its boot is fully seated.
• Start the retaining bolt by hand, then tighten it gently with the matching 8mm or 10mm socket.
• Reconnect the electrical connector until its lock clicks.
• Small coil bolts need very little force.

Step 12: Replace the remaining three plugs

• Repeat Steps 3 through 11 for each remaining cylinder.
• Use the compressed-air blow gun before opening every plug well.
• Torque every spark plug individually to 19.6 Nm (14 ft-lbs).

Step 13: Reassemble the engine cover

• Verify that all four coil connectors are locked and no tools remain in the engine bay.
• Reinstall any brackets using the appropriate 8mm or 10mm socket.
• Align the engine cover with its mounts and press it down evenly, or reinstall its original fasteners.

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✅ After Repair

• Start the engine and let it idle for two to three minutes.
• Listen for a smooth, even idle and watch for a flashing check-engine light.
• Switch the engine off immediately if it shakes badly, misfires, or the warning light flashes.
• If there’s a misfire, recheck every coil connector and make sure each coil is fully seated.
• Take a short, gentle test drive after the idle check passes.
• No spark-plug programming or relearn procedure is normally required.

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💰 DIY vs Shop Cost

Shop Cost: $250-$500 USD equivalent, depending on local parts and labor

DIY Cost: $50-$120 USD equivalent for four plugs

You Save: Approximately $150-$380 by doing it yourself!

Labor prices around Sonīpat can differ considerably from U.S. rates. The job normally takes a shop approximately 1-1.5 hours.

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🎯 Ready to get started?

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