I just purchased this car (09 Hyundai accent hatchback) that was involved in an accident, after we fixed everything and put things back together, my mechanic test drove the car and notice that the car drove nice for couple of minutes and then started to shake bad. He got back to the shop and used the scanner to find a problem with injector 1 (not sure what the code was). After further investigations, we found that injector one will missfire after couple of minutes of starting the car and if you shut the car down and restart the car (even if immidiately) the injector will work fine for another couple of minutes before doing the same thing again. This is the part that we don't understand, why would it work fine if you restart the car??? If there's a problem with the injector, sparkplug or wires or anything else, why would it diappear when re-starting??? Any advice is highly appreciated. By the way, even though the car has only 13k miles, I don't think there is any warranty on the car anymore because of the accident.