when i start up my 3.1 the oil gauge needle (NOT DIGITAL) jumps up as high as it can and stays there. after i drive for a while and then stop at the lights it will sometimes come back to the midranges and bounce around between 1/4 and 3/4 pressure. once i hit the gas again it jumps back up as high as it can go and stays there till the next light. no cluster lights are on. whats the matter with it, adn how do i fix it?