My Audi A4 99.5 has been shaking and there's a loss of power in the engine. The check engine light is on, when the shaking occurs the light flashes, then turns back to just staying consistently on. I've gotten my oil changed and still no difference. I'm trying to sell the vehicle so does anyone know what the problem could be and how much it would cost? I don't know much about cars, so I'm looking for help. Using the money to pay for college and I need to get this car off my hands but no one will buy it while this problem is happening.