I am using my arduino in my car and the LCD (HD44780) is starting to scroll random characters fast when the engine is running. I think this is something voltage related issue. The Arduino Mega 2560 R3 (chinese clone) is connected though the power input socket and it connects to the radio's +12V. When the engine is running it is around 13-14.4Volts, so maybe thats the problem.
Should i use a voltage regulator with capacitors to create a more stable voltage, like 8-10V? Or do you have any other suggestions?