I had this problem a month ago and now it has returned. This happens usually when the car is cold and while I am driving in the morning. I had all fuel injectors with new O-rings put in last year so I doubt its that (maybe the orings are letting it leak again). Anything else I can check because I am getting to a point where if the windows fog up, I will just let it be and not put the defroster on . Turning on heat sucks too because of this gas leak. Thanks.

 

You might be smelling other people's exhaust.

When you defrost you are not using circulated air. It's the Air that's coming from the outside.

 

No, the smell is clearly coming from the engine bay because I can smell it while I am idle. Also today there was no one around me and it stank up the car.