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350Z · Reliability

350Z Spark plugs

Your 350Z

Pick your year so we only show parts that fit your car.

In the US, 2003 350Zs were coupes only and 2009 350Zs were roadsters only. 2003–2006 cars have the VQ35DE engine, 2007–2009 the VQ35HR.

Fixes misfires
Medium$60–$1501.5–3 hrs
All 350Z mods

Why do it

Old plugs cause rough idle, misfires and lost power. Many 350Zs still have plugs that are long overdue. They're cheap, and it's a good first job to learn your engine bay.

Tools you'll need

Parts to buy

Always double-check fitment for your exact year, trim and transmission before buying. Prices change. ModBuddy doesn't earn money from these links.

Before you start

  • Get the right plugs for your engine. 2003–2006 (VQ35DE): NGK PLFR5A-11 for a stock car, or the one-step-colder PLFR6A-11 if you have an intake, exhaust or other engine mods. 2007–2009 (VQ35HR): the OEM HR plug. You need 6.
  • DE engines use a 5/8" plug socket. HR engines use a 14mm thin-wall plug socket, because the plug wells are narrower.
  • Work on a cold engine, and disconnect the negative battery terminal first.
  • The valve covers are plastic. Take your time, never pry against them, and don't over-tighten anything that threads into them.
  • 2007–2009 (HR) cars: the layout is different. You remove the intake tube and throttle body on each side to reach the back coils, like on a 370Z. Watch the extra HR clips on steps 2 and 3.

Video guide

Replacing the spark plugs on my Nissan 350Z
by Dominic Campbell on YouTube

A 2004 (VQ35DE engine) using the NGK OEM-style plugs we list. He tightens the plugs by feel; use a torque wrench instead. 2007–2009 (HR) owners: the extra clips on steps 2 and 3 show the different HR layout. Each ▶ button below jumps to that step in the video.

Watch the whole video

Steps

  1. Remove the strut bar and engine cover

    • Remove the nuts holding the strut tower bar (14mm) and lift it out.
    • Pull the plastic clips on the sides of the engine cover with pliers, remove the four 10mm bolts, and lift the cover off.
    Watch this step (1:50–2:36)

  2. Move the wiring harness out of the way

    • The coil wiring harness is held down by a few 10mm bolts, including one tucked at the back. Remove them so you can lift the harness enough to reach the coils.
    • Take a photo first so you know how it goes back.
    Watch this step (2:16–2:56) 2007–2009 (HR engine): removing the intake tube (shown on a G35 with the same engine) (2:01–3:02)

  3. Remove one coil

    • Work on one cylinder at a time so nothing gets mixed up.
    • Unplug the coil, remove its 10mm bolt and pull it straight up. Coils cost about $100 each, so don't bend or force them.
    Watch this step (2:56–3:17) HR engine: moving the throttle body to reach the back coils (7:09–8:40)

  4. Remove the old plug

    • Blow any dirt out of the plug well first so it can't fall into the engine.
    • Use the plug socket (the rubber insert grabs the plug) on an extension to loosen the plug and lift it out.
    Watch this step (3:17–3:37)

  5. Install the new plug

    • These plugs come pre-gapped. Don't touch the tip or adjust the gap.
    • Thread the plug in by hand until it seats, then torque it to the spec on the plug box or in your service manual. Never start a plug with a power tool.

    Tip: If the plug won't turn easily by hand, back it out and start again. A cross-threaded plug can ruin the cylinder head.

    Watch this step (3:37–3:58)

  6. Refit the coil and repeat

    • Put a thin film of dielectric grease or silicone paste around the inside lip of the coil boot. You only need a little.
    • Push the coil down until it seats, refit its bolt and plug it in. Repeat for the other two cylinders on this side. The last one at the back is the hardest to see, so go slowly.
    Watch this step (3:58–5:10)

  7. Do the other side

    • Remove the 10mm bolts holding the harness on the other side, including the one tucked underneath.
    • Some coils have to come out before you can unplug the next connector. Swap all three plugs the same way.
    Watch this step (5:10–6:11)

  8. Reassemble and test

    • Refit the harness bolts, engine cover, clips and strut bar. Reconnect the battery.
    • Start the engine. It should idle smoothly with no flashing check-engine light.
    Watch this step (6:11–6:31)

How to know it worked

Did this guide work for you?

Safety first

  • Park on flat, solid ground, set the parking brake and chock the wheels.
  • Use jack stands rated for your car. Never get under a car held up only by a jack.
  • Let the engine and exhaust cool completely before touching them.
  • Disconnect the negative battery terminal before unplugging sensors or electrical parts.
  • Wear safety glasses, and gloves around sharp heat shields and hot fluids.
  • Tighten bolts to the torque spec in your factory service manual.
  • If a step doesn't match your car or you're unsure, stop and ask a shop.

These are overview steps written to help you plan the job. Always follow the instructions that come with your part and the procedures and torque specs in your factory service manual. Horsepower is an estimate; results vary.