my tach when you start it up just sits at 4k.. doesnt go much anywhere except up at higher rpms.. what could cause this? even if it did work i understand it wont be that correct but right now im runnin with no tach and its a 5spd.. i cant clock my shifts basically where i wanna shift at.. i have the entire dash pulled all down anyway so i should be able to get to it all.. any ideas? what usually causes these to go out? thanks