engine problems

My car seems to have lost some power, and when i shut it off there is a strong smell of gas im thinking it may be a timing issue anyone have any suggestions on what i should check? Could a faulty o2 sensor make it run bad?

wat kind of car?

unburnt fuel in chamber due to a non-firing cylinder (the smell)? if its NA, do the boy scout thing...check plugs and wires.

95 gs - already did the plugs and wires

If the o2 sensor was bad, you'd most likely get a check engine light.