Mercedes A Klasse Hissing Sound and Check Engine Light

Sounds familiar I had something similar with my A Klasse The hissing and check engine light are dead giveaways It could be a split in the intake hose, happened to me That messes with the air fuel mixture causing your fuel economy to tank Have you tried visually inspecting the hoses for any cracks?

I gave the hoses a quick look, but it's pretty cramped in there Was the split obvious when you found it? How thorough do I need to be with the inspection? Was it affecting your fuel economy noticeably, or was it more of a gradual thing?

Mine was a small split, hard to see at first glance, I had to really bend the hose to see it clearly The fuel economy hit was pretty instant, and the hissing got worse over a few days If you're not sure, I would suggest taking it to a workshop They'll find it pretty quick

Thanks for the insight I'll give the hoses another, closer look Otherwise, I'll just bring it in Turns out the intake hose was indeed leaking Got it replaced, cost me around 100€ Fuel economy is back to normal, and the hissing is gone Check engine light is off too