Citroen Nemo power loss hissing sound

Hey! Sounds frustrating! I had a similar nightmare with my old Vauxhall Astra, a petrol one, though. Same symptoms: loss of power, the jerking, and a weird noise that turned out to be related to the air intake. Have you checked the manifold flap itself? Maybe it's just stuck or gunked up with carbon. A quick clean might do the trick before you start swapping parts. Is the hissing sound coming from the same area, near the manifold?

Thanks for the response. I appreciate the suggestion regarding cleaning the manifold flap. I'm curious about the specific issue with your Vauxhall Astra. Was it also related to the intake manifold flap control, or something else entirely? Also, where exactly was the hissing sound coming from in your case?

Okay, so with the Astra, the hissing was a split in one of the hoses going to the intake manifold – letting air escape. I initially thought it was the flap motor itself, but luckily, it was a much cheaper fix. Given all the symptoms, and that you suspect the flap control, it's probably worth getting it checked out professionally. A proper diagnostic might save you from randomly replacing parts. I ended up going to a local garage because I didn't have the right tools.

Understood. Thanks for sharing your experience and for the advice. I took the vehicle to a local workshop, and indeed, the issue was the intake manifold flap control, which was defective. The repair cost came to 465€. The car runs as expected again.