I have a 99 A6 AVANT with ~93k miles on it. I live in Denver and drove up to the mountains to go skiiing over the weekend. On my way home with the defroster running full blast, I had a very potent gasoline smell coming from the air vents. When I switched to recirculated air the smell went away. When I got back to Denver (~5000ft drop in elev) The problem seemed to have gone away. However, when I started the car up cold this morning I got the same gas smell again from the vents, back to recirculted air and it went away. My Check Engine Light has been on for about a month, but I have never had any gasoline smell from the vents before. I went to autozone to get the code read and it has to do with malfunctioning oxygen sensor(s). Could faulty O2 sensors be causing a gasoline smell to come through my air vents?? Any help anybody could give would be great.

 

I would take off all the plastic covers in the engine bay area and check for leaks.... it would be extremely dangerous for you to drive around with a gas leak... please at least check for that.... You dont want to ignite any leak or fumes. I had a gas leak on a cadillac that luckily had a recall on it... themain line was made of plastic and brokeopen and I had gas spilling all over the exhaust manifold. only thing I would think would be a gas leak... only time you should ever smell gas is when you fill up. Good luck with that,and be safe

 

My thought too is a gasoline leak, but cannot direct you to what causes it in general. An O2 censor may be faulty, but it cannot introduce raw gasoline odor for being faulty.