The 1GR-FE V6 calls for nickel plugs at 30,000 miles. You can run Denso iridium long-life plugs to push the interval out, but plan on pulling the intake plenum to reach the rear three plugs on either choice.
The 1GR-FE 4.0L V6 in the 4th and 5th gen 4Runner has been one of Toyota's most reliable engines, but Toyota specced it with nickel-copper plugs and a short 30,000-mile interval. That short interval is the price you pay for getting at the rear three plugs — they sit underneath the upper intake plenum, and reaching them means removing six plenum bolts, the throttle body harness, and the PCV hose. Many owners buy iridium long-life plugs once and skip the chore for the next 100,000 miles.
OEM front-three plugs are Denso K20HR-U11 (Toyota 90919-01235) or NGK LFR6C11 (Toyota 90919-01236) — both nickel. The factory-equivalent iridium upgrade is Denso SK20HR11 (Denso #3438), which fits identically and runs roughly 100,000 miles. Gap spec is 0.043" (1.1mm) — verify with a feeler gauge on every new plug, even iridium pre-gapped sets, because shipping drops happen.
The front three plugs are manageable: pop the coil pack cover, unbolt each coil with a 10mm, lift it out, and pull the plug with a 5/8" deep socket on a long extension. Twenty minutes total. The rear three are the actual job. Sequence matters: disconnect the throttle body connectors, the EVAP line, the PCV hose, the brake booster vacuum hose, and unbolt the upper plenum (six 12mm bolts). Lift the plenum off, set it aside on a clean shop rag, and inspect the gasket — if it is the original rubberized gasket, replace it now (Toyota 17171-31040, about $35).
Torque the plugs to 13 ft-lb (17.5 N·m). The 1GR-FE uses 14mm plugs, but the same caution applies as any aluminum head — go past 18 ft-lb and you risk pulling threads. No anti-seize on the plug threads (Denso and NGK both say not to). A dab of dielectric grease in each coil boot keeps the boot from sticking the next time.
Reinstall the plenum with a fresh gasket if you pulled the old one. Hit each bolt in a crisscross pattern at 18 ft-lb. Reconnect every harness, hose, and clip you removed. Disconnect the battery for 5 minutes before reconnecting to force the ECU to relearn idle on first start.
| Part | Vendor | Est. price |
|---|---|---|
| Denso K20HR-U11 nickel (set of 6) — OEM | Toyota / Denso | ~$45 |
| NGK LFR6C11 nickel (set of 6) — OEM alt | Toyota / NGK | ~$42 |
| Denso SK20HR11 iridium long-life (set of 6) — extended interval | Denso | ~$90 |
| Dielectric grease | Permatex | ~$4 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.