Peugeot 407 engine stalling idling

I had something similar with my 407. Does it seem to happen more when the fuel tank is full or nearly empty? Could be the fuel tank ventilation system. Check for any hissing sounds around the fuel filler area when the engine is running. I'd suspect the charcoal canister.

Yes, I have observed it lately when the tank is almost full. Hissing, you say? Where exactly is the charcoal canister located, and is it easy to get to for a quick check?

Yeah, near the fuel tank, part of the ventilation system. Honestly, I wouldn't mess with it too much yourself unless you know what you're doing. A leak in that system can cause all sorts of weird fuel efficiency and system failure problems. Best to take it to a workshop to get it properly diagnosed. They'll have leak detection tools. It's probably a defective activated charcoal filter.

I took it to a local mechanic, and you were spot on. Turns out it was the activated charcoal filter. They replaced it, and the check engine light is gone, and the stalling has stopped. Cost me 275€, but worth it for the peace of mind!