I have a 1995 mustang gt and when i start it the rpm needle stays all the way down as if it's not responding. but if i give it a lot of gas it will jump up right away to about the 5k range and when i let off the gas it comes down to about 900. and at normal driving speeds it stays at about 900. i know that the idle is not correct and the display of 900 is not correct. what can be causing this problem?
I would have to agree with ol steve down there but seriously your tac is messed up buddy, you need to follow the wires form the distributor to the Tachometer. ether a loose connection of a wire or the Tac itself or you just need to replace it.