VW Jetta Hybrid Power Loss Due to Air System Issues

Had a similar issue with my 2014 VW Passat Hybrid last year. Having some experience with hybrid systems, I recognized the symptoms immediately as they matched what you are describing, rough idle, power loss, and check engine warnings. The main problem turned out to be a faulty hose connection between the pump and air valve, which was affecting the manifold pressure and throttle body response. These connections are critical for proper air intake management. Took it to my regular workshop and they diagnosed it quickly. The repair involved: Full diagnostic scan, Pressure testing of the system, Replacement of the defective hose connection, Recalibration of the throttle body sensors Total cost was 175€ and they completed everything in about 3 hours. The check engine light cleared up immediately and the engine ran smooth again after the fix. Before suggesting more specific advice, could you share: Any diagnostic codes you have pulled? When does the rough idle occur (cold start, warm engine, or both)? Have you noticed any unusual sounds from the engine bay? Any recent maintenance work done? This information would help determine if your issue is identical to what I experienced with my VW.

Thanks for the detailed response. The issue started right after my last service at 97574km. The rough idle occurs mainly during cold starts, accompanied by a slight whistling noise from the engine bay. I pulled the codes using an OBD scanner and got P0106 (Manifold Pressure Sensor Circuit Range/Performance) and P2279 (Intake Air System Leak). The throttle body and air supply system were actually checked during my recent service, but the problems started shortly after. The symptoms match what you described with your Passat. Based on your repair details, I will have the workshop focus on checking those specific hose connections. The 175€ repair cost seems reasonable if it solves these idle problems completely.

Looking at your diagnostic codes and symptoms, this confirms my initial thoughts about the manifold pressure issues. After getting my Passat fixed last year, I actually encountered a similar whistling noise again about 2 months later, but it turned out to be a different yet related problem. The second time, the issue was caused by a hairline crack in the air intake manifold itself, not just the hose connections. The throttle body was getting inconsistent air supply readings because of this tiny leak. Since you mentioned the issues started after service, I would definitely have them check if any components were inadvertently stressed during the maintenance work. In my case, the complete fix for the second issue included: Air intake manifold replacement, New gaskets, Air valve system pressure test, Full system calibration The repair cost was higher than my first fix at 320€, but it permanently resolved both the whistling noise and irregular manifold pressure readings. Workshop time was about 4 hours. The matching error codes between our cases strongly suggest you are dealing with the same type of air supply system problem. I would specifically request they inspect both the hose connections and the manifold body for any stress cracks or damage.

My concerns about the whistling noise and error codes match what you experienced. The starting issues after the service definitely seem connected to the air supply system problems you mentioned. The vacuum hoses and manifold pressure issues you encountered with your Passat sound very similar. At those repair costs, getting both the connections and manifold body checked makes sense, especially since my idle problems started right after the service work. I will book the car in and ask them to specifically check the points you mentioned. Will make sure they do a complete pressure test of the air valve system and inspect for those hairline cracks you found. The 320€ cost seems worth it if it fully resolves these symptoms like it did in your case. Thanks again for sharing the detailed repair information. This gives me a much clearer picture of what to expect at the workshop regarding both the diagnosis and repair process.