The 2008 Nissan Altima 2.5L plugs are accessed by removing the engine cover and ignition coils, torqued to 14.5 ft-lbs every 105,000 miles.
How to replace spark plugs in a 2008 Nissan Altima depends on which engine you have — the 2.5L QR25DE version is a straightforward one-hour job, while the 3.5L V6 requires intake manifold removal. This guide covers the 2.5L four-cylinder procedure: four plugs, four coils, and a 14mm deep-well socket stand between you and a smoother-running engine. Doing it yourself saves $80–130 in labor compared to a shop charging $130–180 for the full job.
What Tools and Parts Do You Need?
You need four spark plugs — Denso FXE20HR11 (OEM) or NGK DILKA-R6A-11 — along with a 14mm deep-well spark plug socket, a 10mm socket for the coil bolts, a 5mm hex bit for the engine cover, and a torque wrench. Genuine Nissan plugs (part 22401-1KT1B) run about $12–18 each from dealers, or you can save with NGK equivalents. Check our roundup of the best 08 Nissan Altima spark plugs for current pricing and recommendations. Replacement plugs are the same across most Nissan models using the QR25 engine, so stock is usually easy to find.
| Item | Specification | Note |
|---|---|---|
| Spark plug (OEM) | Denso FXE20HR11 (22401-1KT1B) | 4 plugs needed; ~$50–70 dealer |
| Spark plug (alternative) | NGK DILKA-R6A-11 | ~$35–50 for a set of 4 |
| Spark plug socket | 14mm deep-well | 5/8″ socket will not engage correctly |
| Torque wrench | Required for installation | Plug: 14.5 ft-lbs; Coil: 5.2 ft-lbs |
| Socket set | 10mm + 5mm hex | Plus a ratchet extension |
| Plug removal aid | Magnetic puller or old coil boot | Plug may not drop out on its own |
Step-by-Step Replacement Procedure
The whole job takes about an hour for a first-timer. Work on a cool engine and disconnect the battery first. Nissan’s official maintenance schedule recommends replacement every 105,000 miles or 7 years.
1. Disconnect the battery. Use a 10mm socket to loosen the negative battery terminal and set the cable aside. This prevents accidental sparking and electrical shorts.
2. Remove the engine cover. Locate the three 5mm hex bolts on the plastic cover. Remove them and lift the cover straight off.
3. Disconnect the ignition coil harnesses. For each of the four coils, press the tab on the wiring connector and pull it off. A small flat-blade screwdriver helps if it is tight. Never pull the wires themselves.
4. Remove the ignition coils. Use a 10mm socket to remove the single bolt securing each coil. Lift the coil straight up and out. If the engine harness blocks removal, unclip it from the bracket with pliers.
5. Extract the old plugs. Insert a 14mm deep-well spark plug socket with an extension and turn counterclockwise to break each plug free. If the plug does not drop into the socket, use a magnetic puller or gently insert the old coil boot to grip and lift it out.
6. Install the new plugs. Thread each new plug into the cylinder by hand to avoid cross-threading. Once it seats, use a torque wrench set to 14.5 ft-lbs. The factory gap (0.044 inches) is preset on OEM plugs — do not adjust it. If using aftermarket plugs that are not pre-gapped, check and set the gap before installation.
7. Reinstall the ignition coils. Lower each coil into position, install the 10mm bolt, and tighten to 5.2 ft-lbs. Reconnect each wiring harness by pressing until the tab clicks.
8. Replace the engine cover. Reattach any harness clips you removed, align the cover, and secure it with the three 5mm hex bolts. Tighten snugly — no torque wrench needed here.
9. Reconnect the battery. Reattach the negative terminal and tighten with a 10mm socket.
Common Mistakes and Safety Tips
The most frequent error is using a 5/8-inch (16mm) socket instead of the required 14mm deep-well socket — it will slip or damage the plug. Always hand-start threads on new plugs to prevent cross-threading, which ruins cylinder head threads and requires expensive repairs. Over-torquing past 14.5 ft-lbs can crack the ceramic insulator or strip threads, so use a torque wrench even if you are experienced. When pulling ignition coils, press the connector tab and pull the connector housing — pulling the wire can break the internal connection. If the old plug feels stuck, a little penetrating oil around the base and a few minutes of waiting can help break it free. Finally, confirm you have the 2.5L QR25DE engine before starting; the 3.5L V6 in the same model year needs intake manifold removal and a different procedure.
Doing it yourself saves most of that cost and takes about an hour with the right tools.
FAQs
How often should spark plugs be replaced in a 2008 Altima?
Nissan recommends replacing spark plugs every 105,000 miles or 84 months (7 years), whichever comes first. If you notice misfires, rough idling, or reduced fuel economy sooner, check the plugs even if you have not hit that mileage.
What happens if I use the wrong socket size?
Using a 5/8-inch (16mm) socket instead of the required 14mm deep-well socket will fail to engage the plug hex properly, rounding it off or slipping. Always verify you have a 14mm metric deep-well spark plug socket before starting.
Can I replace plugs without a torque wrench?
Not recommended. Over-tightening can crack the spark plug insulator or strip the cylinder head threads. Under-tightening can cause the plug to loosen and misfire. A torque wrench set to 14.5 ft-lbs is the only reliable way to get it right.
References & Sources
- Nissan. “2008 Altima Spark Plugs — Maintenance Schedule.” Official replacement interval and service recommendations.
- Kelley Blue Book. “2008 Nissan Altima Spark Plug Replacement.” Estimated labor and parts cost guidance.