My 2013 optima engine stalls every time I attempt to start it for the past year. I've taken it to the dealership and they say there are no codes. After leaving it for several days they suggested I replace the feul pump which I did. That did not help. They suggested the Trottle body be cleaned, which I did. That also did not help. Im spending a lot of money and still there's no resolution. Can you help?