When I start my 1999 Honda Civic, a sort of sulphury smell comes through the vents. I ended up having my compressor replaced today, and I assumed the smell would be clean, because the a/c is new. (Tells you I don’t know much.) Anyway, the smell is still there, along with a smell from the oil (I have a small oil leak) and engine. It all goes away after a minute or two, but is this anything to worry about?
It sounds as though you may have a small exhaust leak somewhere and you’re smelling exhaust fumes from the startup. It could be dangerous if enough exhaust fumes are leaking into the cabin. If you’re leaking oil onto the engine and it’s getting on the hot exhaust manifold, you’re going to keep smelling that until you get the oil leak fixed.