my car didnt come with a tach.. went to the junkyard as you did. had to do some soldering, but i had the same problem as you did. all you have to do is, start the car without the needle on the tachometer, then shut it off. then put the need back on while the car is shut off, make sure its at zero as you're sticking it back on. then start the car, and it should idle fine...at least thats what i did.....my idle is about 800-1000 rpms