It happens more often than you think. I work in the auto parts industry and I sell several a month. From what I've been told, the secret is routine oil changes, no more than 5000 miles and run some cleaner through the throttle body to break up carbon deposit buildup on the valves. Seafoam makes a kit to do this. Advance Auto parts carries it. The technicians in my area recommend it be done about every 6 months.