i just bought a 92 Si hatchback from a friend of mine. everything seemed fine for a couple days. today the tachometer went sketchy. it works fine when in neutral, responds to reving it up , but as soon as i put it into gear, it drops to zero and stays there. car seems to run fine otherwise, sound like its struggling a little when starting. i dont know much about how this all works, but im trying to learn. any help at all would be great... thanks

 

Sounds like the speed sensor is going out. You can get one for like $25 at a salvage yard. Located on the left side of your engine on the trans mount. Looks like this...