In my 2003 Opel Vectra, the cabin air smells of Diesel exhaust while stopped at e.g. a red light.
The exhaust smell goes away when driving, and it also doesn't come back if I turn the ventilation off before stopping at a light. It's not temperature-related: it happens whether it's cold or warm outside, and also whether or not the engine has reached its normal operating temperature. It also happens whether or not the A/C function of the ventilation system is turned on. The car's windows are always closed.
It seems to me that there is some problem with the car's ventilation and/or exhaust system. I'm fairly sure it's not a problem with the A/C itself as it's not a chemical odor but clearly an exhaust smell.
Asking the dealer, he told me that the car has a Diesel-powered auxilary heater that engages when it's cold outside and the engine isn't warm yet. While that heater is working, the heated cabin air might have a weak Diesel smell.
- This explanation would make sense to me if it didn't happen in the summer too (when the aux heater is presumably not used), and if it did happen while driving, but neither is the case.
1. What could be wrong with the car?
2. Is it dangerous to drive? (carbon monoxide gases)