Howdy, im attempting to wire a tach into my 93 ranger. its the 8 plug 2.3 with all the coil pack things on it. now the tach has 4 wires, red, black, green and white. i know the white one is for the light in it, blacks my ground, but not sure what that green one does or where to hook up my red. each set of packs has 3 wires going to them and i tried hooking it in to all 6 wires, at seperate times, and it works while im at idle but as soon as i give it gas the tach just drops. take my foot off the gas and it will jump to the rpm i was at and fall with it and it seems accurate, but why does it do this?