Vauxhall Adam rough idle

Rough idle and check engine light, huh? Vacuum leak is a definite possibility! Does it happen mostly when the engine is cold, or does it persist even after it warms up? Have you tried visually inspecting any of the hoses around the engine bay? Sometimes you can spot a crack or a loose connection. It could also be related to the throttle body. Is it dirty? Do you have any idle problems? I am just thinking aloud...

Okay, thanks for the ideas! Yeah, the rough idle seems worse when it's cold, but it doesn't totally go away when it warms up. I had a look at the hoses, and nothing obvious jumped out. What exactly should I be looking for regarding the throttle body?

Okay, so worse when cold could point to a vacuum issue getting temporarily sealed as things warm up and expand slightly. As for the throttle body, check if it's covered in gunk. A dirty throttle body can mess with the airflow and cause all sorts of issues. But honestly, without proper diagnostics, you might just be chasing your tail. Have you considered taking it to a trusted mechanic? They could hook it up to a diagnostic tool and pinpoint the problem in no time.

You were spot on! Took it to the shop, and turns out it was a defective hose connection from the pump to the air valve. Cost me 175€ to get it sorted. Runs like a dream now! Thanks for pointing me in the right direction!