How old is the O2 sensor? If you don't know, I would replace it first before fiddling with the mixture setting. If you car is running right, and fully warmed up, the exhaust should have very little or no odor.

Adjusting the mixture will require some studying - search this website for that, and a mulitmeter with a duty cycle function.

__________________
1985 380SE Blue/Blue - 230,000 miles
2012 Subaru Forester 5-speed
2005 Toyota Sienna
2004 Chrysler Sebring convertible
1999 Toyota Tacoma