Parts for your 2004 Toyota Highlander-Fuel injectors

2004 Toyota Highlander fuel injectors

Per Toyota service information (TIS) for the 2004 Highlander/Harrier, both the 2.4‑litre 2AZ‑FE and 3.3‑litre 3MZ‑FE engines run electronic sequential multi‑port fuel injection, with one injector per cylinder. Toyota’s New Car Features manual for the model year, along with OEM parts catalogues and mainstream workshop manuals, all confirm this. So yes—fuel injectors are very much used on the 2004 Toyota Highlander.

On this Highlander, the fuel injectors’ job is to deliver precisely measured petrol into each intake port at the right moment, as commanded by the engine control unit using feedback from the air‑fuel ratio and oxygen sensors. Being port‑injected (not direct‑injected), the injectors sit in the intake manifold with rubber O‑rings and insulators to keep things sealed and quiet. This setup helps cold starts, smooth idle, decent fuel economy and low emissions when everything’s in good nick.

They’re not a regular “service item” with a fixed replacement interval, but they do benefit from sensible care. Using quality petrol, keeping up with engine air filter and spark plug changes, and running a periodic detergent fuel system cleaner containing PEA can help keep spray patterns tidy. Many owners opt for professional flow‑testing and ultrasonic cleaning somewhere between 150,000 and 200,000 kilometres if there are symptoms.

Common signs of injector issues include rough idle, hard starting, poor fuel economy, a fuel smell, or fault codes like P030x misfires or lean/rich mixture codes. Because vacuum leaks, coil packs and plugs can mimic injector faults, proper diagnosis is worth its weight in gold before throwing parts at it.

When replacement is needed, best practice is to install new upper and lower O‑rings and insulators, lightly lubricate the seals, and carefully seat the injectors to avoid nicks. Always depressurise the fuel system, disconnect the battery and check for leaks on restart. The 4‑cylinder 2AZ‑FE offers relatively straightforward access