Lexus GX Hybrid Air Intake Leak

Hey there! Sounds frustrating. Those symptoms definitely point towards an air leak somewhere after the mass airflow sensor. I had a similar experience with my old Subaru Outback – check engine light, the works. It turned out to be a cracked vacuum hose connected to the intake manifold. Basically, unmetered air is getting into the engine, throwing off the air/fuel ratio and making it run lean, which explains the poor fuel economy and the check engine light. The hissing is likely the sound of the air being sucked in. Have you specifically looked at the intake hose between the air filter box and the throttle body?

Could you elaborate on the location of the intake hose and what I should be looking for in terms of damage? I am not very experienced with automotive repairs, but I am willing to investigate further before taking it to a professional.

No problem! The intake hose is that big, usually black, rubber or plastic hose that connects directly to the air filter box on one end, and then goes to the engine's throttle body (where the engine sucks air in) on the other. Look for cracks, splits, or loose clamps, especially near the ends. Even a small crack can cause those symptoms. Honestly, though, if you're not super comfortable poking around, it might be best to take it to a trusted mechanic. They can do a smoke test to pinpoint any leaks quickly.

I appreciate the detailed explanation and advice. I'll schedule an appointment with a certified Lexus technician to diagnose and repair the potential air intake leak. It sounds like it is beyond my capabilities. The workshop confirmed that the intake hose was leaking and replaced it for 100€.