So glad to find this thread, thought I was going insane, or sitting on a stroke. I've also been smelling car fumes/exhaust, and/or a dusty smell (mostly this), for about a week now.
I've had acid reflux for years, drink diet drinks with Splenda (occasionally), have had sinus infections in the past, and use a sinus rinse regularly, but never experienced this until recently. The only change I can think of, is a recent change in my sinus rinse (changed the salt I use) which maybe damaged(?) my sinuses. I kind of wonder if it's like when burning you tongue and can't taste anything for a few days.
The smell does only become noticeable when breathing normally (not necessarily shallow), and does go away when breathing deep. I'm also baffled why it's so much stronger when sitting or laying down. I noticed it where ever I'm sitting (home, work, car, etc.).
I've tried decongestants (generic Sudafed) and 24 hour allergy (generic Claritin), mint tea, ginger, and Vicks. None of them seem to help. It seems to be better after getting out of the shower, until my nose dries out. I'm trying holding off on further nasal rinses for a while to see if that lets things clear up. I'm wondering if I've got a cold/flu/sinus infection starting since I also seem to have a bit of a sore throat and occasional stuffy nose. There don't seem to be any other symptoms though.
I've always had a really good sense of smell. Really hope this goes away on it's own. Extremely annoying and makes me worried I'm going to suffocate from a gas leak I can't smell. Promise to post updates, if anything changes.