H1 Intake Manifold Flap Control Issue

Sounds familiar. I had similar symptoms in my H1: reduced power, rough running, hissing…the whole shebang. Have you checked the intake system for leaks or damage? Specifically, look at the actuator arm for the intake manifold flaps; those are known to cause problems with airflow control. What diagnostic steps have you taken so far besides noticing the symptoms?

Thanks for the quick reply. I haven't dug too deep yet, just checked for any obvious loose connections or broken hoses in the air intake. I was hoping it was something simple. You mention the actuator arm, is that something easily accessible to inspect without tearing half the engine apart?

Yes, the actuator arm is reasonably accessible, though it depends on your mechanical aptitude. However, based on the symptoms and your initial assessment of the intake manifold flap control, it's likely the switch itself is defective. Given the symptoms, I'd advise getting it professionally diagnosed rather than chasing it yourself. I ended up at the workshop because I didn't have the right tools. They said the flap control was defective.

Appreciate the confirmation and advice. Sounds like a trip to the workshop is in order. I'll post the diagnosis. It was exactly what was suggested - the intake manifold flap control switch was indeed defective. Cost me 465€ to get it sorted, but the H1 is running like new again.