Peugeot 4007 Intake Manifold Flap Issue

Those symptoms certainly suggest a potential issue within the intake system, specifically the intake manifold flap control. The combination of reduced power, rough running, and hissing noise points towards a possible malfunction affecting airflow. Is the engine light on? Has a diagnostic scan been performed to retrieve any stored error codes? Knowing these codes would greatly assist in pinpointing the exact nature of the problem.

Yes, the engine light is on. I haven't done a diagnostic scan yet. Would you recommend a specific type of diagnostic tool or procedure to effectively read the error codes related to the intake manifold flap control? Are there specific codes I should be looking for?

Given that the engine light is on, a diagnostic scan is definitely the next step. Any standard OBD-II scanner should be capable of retrieving the necessary codes. Focus on codes related to the intake manifold, throttle body, or air intake system. While I can't definitively say without the codes, based on your description and the year of the vehicle, it's quite likely the intake manifold flap control switch is defective. However, I would strongly advise consulting a qualified workshop for a comprehensive diagnosis. They will be able to confirm the fault and advise on the appropriate repair procedure.

Based on your recommendation, I took the Peugeot to a trusted workshop. The diagnostic scan confirmed that the intake manifold flap control switch was indeed defective, as you suspected. The repair, including parts and labor, amounted to 465€. The vehicle is now performing optimally. Thanks again for your assistance.