Engine Light On (Censor Trouble)

Hey guys. My sisters car is having some troubles. Its a Mazda Protege 2004 and whenever you are driving the engine light is blinking. The car goes realy slow and the engine rev's up pritty loud. The car can only top out at 45 mph. And whenever i drive it and come to a stop the car shakes and vibrates almost. But sometimes if you turn the car off and back on it will work fine for about 3 minuets then it acts up again.

HELP PART:

1. What is the problem
2. How do i fix it.