Espace hissing sound and fuel consumption

I had similar symptoms on my Espace. High fuel consumption, check engine light... sounds like you've sprung a vacuum leak. The hissing is a dead giveaway. Check all your hoses connected to the intake manifold and throttle body. It's like a balloon with a pinhole – that's where the hiss comes from. Start with the easy stuff first.

Thanks for the quick response. Where exactly should I be looking? Are there any hoses in particular that are known to fail? I'm not super experienced, so any specific pointers would be appreciated.

Without seeing it, it's hard to say exactly. But yeah, vacuum hoses are a common culprit, they get brittle and crack. Given your symptoms, I'd advise taking it to a workshop. My issue ended up being a cracked intake hose, cost about 100€ to repair. They'll do a proper leak detection test.

Thanks for the advice. I took it to a workshop, and you were spot on – it was a leaking intake hose. They replaced it, and the hissing is gone, fuel consumption is back to normal, and the check engine light is off. Cost me 100€ as you predicted. Appreciate the help!