Driving my 2001 W203 C240, starts to loose power, hiccups a few times, check engine light goes on, no info or malfunction screen. Pull over, stalls, remove key and reboot, idles smooth then rough then smooth again, check engine light still on. Remove key, r&r gas cap, wait 10 minutes, same problems. Limp home, can travel at smooth slower pace, but stalling out twice as result of accelerating. Call "I" button, and he says probably bad gas. Gas tank half full, stop on way to fill up in case it's bad gas, but why did I go thru half tank of bad gas first? Anyway, adding gas doesn't change. What do you think my problem is?