Parts for your 2004 Toyota Highlander-Spark plugs

2004 Toyota Highlander (Kluger) spark plugs

Per Toyota’s owner’s manual and scheduled maintenance guide for the 2004 Highlander (sold as Kluger in Australia/New Zealand), both the 2.4L 2AZ‑FE four‑cylinder and 3.3L 3MZ‑FE V6 are petrol engines that use iridium spark plugs. This is echoed in Toyota service literature and OEM parts catalogues from Denso and NGK. So yes—spark plugs are absolutely relevant on the 2004 Toyota Highlander/Kluger.

On this model, spark plugs ignite the air–fuel mix inside each cylinder, kicking off combustion thousands of times a minute. Healthy plugs help it start quickly on chilly mornings, idle smoothly at the lights, pull strongly up hills, and keep fuel economy and emissions in check. Toyota specifies long‑life iridium plugs for this generation, which are designed to last far longer than traditional copper plugs.

As part of routine servicing, spark plugs deserve a spot on the checklist. Toyota typically rates its iridium plugs for around 160,000–192,000 km (about 100,000–120,000 miles), but real‑world conditions matter—short trips, dusty roads, or heavy towing can bring the interval forward. When they’re tired, the Highlander/Kluger may show:

• Hard starting, rough idle, or a stumble on acceleration
• Higher fuel use and a drop in power, especially under load
• Misfire codes and a flashing check engine light if it’s bad enough

When replacing, stick with OEM‑equivalent iridium plugs specified for the exact engine. Work on a cold engine, blow debris out of each plug well, and torque to factory spec—over‑tightening can damage threads, under‑tightening can cause leaks. Iridium plugs are usually pre‑gapped, avoid forcing the ground strap to change the gap. A few handy tips:

• Replace all plugs as a set and inspect coil boots, swap any that are cracked or oil‑soaked
• Avoid anti‑seize on modern nickel‑plated plug threads, it can lead to over‑torque
• 2.4L 2AZ‑FE: straightforward access, allow time to clean the wells properly
• 3.3L 3MZ‑FE V6: the rear bank is under the intake manifold, manifold removal is usually required—many owners leave this to a pro
• If plug wells show engine oil, the tube seals or rocker cover gasket may need attention

Keep a record of the date, odometer, plug brand/code, and any coil replacements. Done right, fresh plugs make the 2004 Highlander/Kluger feel crisper, start easier, and run more efficiently across Aussie and Kiwi roads.

How often should spark plugs be replaced on a 2004 Toyota Highlander (Kluger)?

With the factory iridium plugs, expect around 160,000–192,000 km (100,000–120,000 miles) under normal driving. If you do lots of short trips or towing, check earlier. Always follow the interval on the under‑bonnet label or in the owner’s manual for your engine (2AZ‑FE or 3MZ‑FE).

What type of spark plugs does the 2004 Highlander/Kluger use?

Toyota specifies long‑life iridium plugs from reputable makers (commonly Denso or NGK) matched to the engine’s heat range and thread. The gap is typically around 1.0–1.1 mm and usually pre‑set—don’t force an iridium plug to change the gap. Use the exact part number listed for your engine.

Can a home mechanic change the plugs on this model?

On the 2.4L four‑cylinder, yes—access is fairly straightforward with basic tools. On the 3.3L V6, the rear bank sits under the intake manifold, so the job is more involved. If you’re not confident removing the manifold and re‑sealing everything properly, a trusted technician is the safer bet.