A sharp hiss at idle with a rough, hunting engine. A cracked hose letting air sneak in.
A cracked vacuum hose, a leaking intake gasket, or a stuck purge valve.
Cheap to hunt with carb cleaner or a smoke test. Lean codes plus hiss is your confirmation.
Reading about sounds only goes so far. The tuner on our home page listens in your browser and tells you what it hears. The app goes further: it names the exact fault, checks it against your vehicle, and tells you how urgent it is.