Skoda Rapid high fuel consumption and hissing sound

High fuel consumption and a hissing sound? Sounds like you have a vacuum leak somewhere. The check engine light probably came on because of an engine misfire caused by the lean mixture. I had a similar problem with my Rapid, although I didn't get the hissing. First, check all the vacuum hoses, especially the one connected to the throttle body and the air filter housing. Those are prone to cracking. Think of it like a punctured bicycle tire, you need to find the hole to fix it.

Yeah, I figured it might be a vacuum leak, but I'm not super familiar with where all the hoses are. When you say 'the one connected to the throttle body', could you be a little more specific? Is it easy to spot, or is it tucked away somewhere? Also, could a bad air filter cause similar symptoms?

Okay, so on my Rapid, the vacuum hose I'm talking about is fairly easy to see. Pop the hood, and look near the throttle body (where the air enters the engine). There's usually a small, rubber hose connected to it. Give it a good squeeze and check for cracks. Regarding the air filter, a clogged one could contribute to poor performance, but it wouldn't usually cause a hissing sound. That really points towards a leak. Honestly, if you're not comfortable poking around too much, it might be worth taking it to a mechanic for a quick leak detection test. Could save you a lot of guesswork.

Thanks again for the heads up. Took it to a shop, and you were spot on. Turns out it was a vacuum hose with a massive leak. They replaced it, did a leak detection test to be sure, and the car is running smooth again. Cost me around 100€, which isn't too bad. No more check engine light or hissing! Appreciate the help!