I have a 05 Stratus 2.4L DOHC and most of the time it runs great, but increasingly the engine light has been coming on and the car struggles to get from 1st to 2nd gear. Upon hitting 2000 rpm it shutters and hesitates and I can't get it above 30. There have been a few times where it has failed to start right away. I've taken it to a mechanic, but it doesn't seem like anyone can figure out what's wrong. The problem is intermittent so it acts up for me, but never when its in the mechanic's hands. I feel like I'm wasting their time, but I know something is wrong. Any ideas?