1997 Nissan Altima Timing Or Bad Gas

I was driving my car after filling up with regular gas and I accidentally shifted from 1st to 4th the car shut off and then ran with a rough idle and sometimes shutting off. Mechanic says it might be bad gas and it wouldnt run if timing was off. Checked gas and gas was yellow in color and smelled very weak. Could timing belt have jumped a couple of teeth or is gas probably bad?