C8 Hissing Sound Fuel Consumption

My 2007 Citroen C8, gasoline engine, has increased fuel consumption, a check engine light, and a loud hissing sound when I accelerate. It's done 108390 km. I suspect an air intake system leak, possibly a leaking intake hose. Should I be checking something else, like engine misfire, vacuum hose, air filter, or throttle body?

4 comment(s)

That sounds like a vacuum leak. Have you checked all the hoses connected to the intake manifold? Even a small crack can cause havoc. It might be a cracked or loose hose.

I did a visual inspection of the hoses, but it's difficult to spot small cracks. Did you find the leak yourself, and if so, how?

I couldn't locate the leak myself. I took it to a workshop, and they diagnosed a split in one of the intake hoses using a smoke test. For the relatively low cost, it might be a good idea to take it to your local shop.

I brought it to a local mechanic. They confirmed it was indeed an intake hose leaking. The repair cost me 100€, including parts and labor. The fuel consumption is back to normal, the hissing is gone, and the check engine light is off. Thanks for your help!

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