What might be the cause? on 1998 Nissan Altima

My car started to run rough. It started blow white smoke and i could smell gas. My car stalled out, the check engine light came on. The car did not over heat. The car will not restart. The computer says Misfire cylinder 3.

Asked by for the 1998 Nissan Altima
poss plug,coil or injector issue,seek diag