I have a 2015 Fiat 500L. In the past few weeks I have noticed a smell in the cabin when stopped at a signal. I can also see vapor type puff coming from the engine compartment at the same time when the smell starts. I have checked all fluids, and there are no warning lights on the dash when this happens. All instrument indicators look normal. This doesn't happen every time or even every trip. It's hard to describe the smell, it's kind of like you passed a char broiled hamburger place. The air conditioner has been on every time because I live in Southern CA and it's been hot. The air conditioner seems to still be working fine so I doubt if it's the AC coolant leaking. If anyone has had a similar problem and knows the cause I would greatly appreciate a response.