Vios Engine Stalling Idling

I had a similar problem with my Vios. Those symptoms sound like a fuel volume regulator issue. The reduced engine power and stalling at idle are classic signs. Could also be the high pressure pump, which controls the fuel pressure going to the fuel injectors. Check if the fuel economy has worsened.

Thanks for the quick reply! A fuel volume regulator? I hadn't considered that. How did you figure out that was the problem? And was it difficult or expensive to fix? Fuel economy has definitely taken a hit, now that you mention it. I'm just trying to get an idea of what I'm in for before I take it to a mechanic.

Given the symptoms, especially with the fuel economy drop, it strongly points to the fuel volume regulator, which might be related to a defective high pressure pump. I had mine checked by a professional, and they confirmed it with diagnostic tools. I recommend you do the same before replacing any parts. You don't want to start throwing money at it randomly. Just take it to a workshop.

Thanks a lot for the advice! I took it to the shop, and you were spot on. Turns out the fuel volume regulator was indeed defective, likely caused by the high pressure pump failing. The repair cost me about 1510€, but at least it's running smoothly again. Really appreciate the help!