190E gas smell from exhaust

[ivanlee190e]

190E '88 2.3 8v. I have lately begun to smell gas when the engine is on, especially in cold mornings. To be a little more exact, the smell seems like unburnt "crude" gasoline that indicates a rich mixture. I can smell this odor with the windows open but I never never smell this with the engine off, only with engine running. The smell is not too bad, but I can notice it and ask my relatives and friends if they can smell it. Most of the time they say no but a few have complained that my car smells when runs.

Besides a rich mixture, what could be other causes? Oxygen sensor bad??? a leak in the fuel delivery system? Any ideas on unburnt gas smell while car is running will be appreciated.