Tahoe Diesel Intake Manifold Flap Issue

Yep, those symptoms scream intake manifold flap issues. The hissing is likely air leaking past a poorly sealed or malfunctioning flap. Reduced power and rough running are classic signs of incorrect airflow, as the flap isn't properly controlling the intake air. The jerking could be the engine management system trying to compensate for the irregular airflow. Have you tried visually inspecting the intake manifold area for any obvious cracks or loose connections? Also, what were the exact error codes?

Thanks! I appreciate the insights. I visually inspected the intake manifold area, but I didn't see any obvious cracks or loose connections. I'll have to check the error codes again, but I remember something about the position sensor. Could a faulty position sensor cause these symptoms even if the flap itself isn't mechanically damaged?

Absolutely, a dodgy position sensor will cause those issues. The ECU relies on that sensor to know the flap's position and adjust accordingly. If the sensor is feeding incorrect data, the flap won't operate correctly, even if the flap motor is fine and the manifold isn't cracked. That said, with those kilometers, it's not uncommon for the flap motor itself to fail or the linkage to become worn. At this point, I'd advise a trip to a reputable workshop. They can properly diagnose the sensor, motor, and linkage. They can also check for carbon buildup that might be restricting the flap's movement. It might be a relatively simple fix, but best to get it sorted before it causes further damage. Continuing to drive like that can't be good for engine performance or fuel economy. Good luck!

I appreciate the detailed advice. It seems a trip to the workshop is the best idea. The mechanic confirmed that the switch intake manifold control was defective and replaced it. The repair cost was 465€. Thanks again for your help!