Factory tach problem
 

I have stock '92 GT and the factory tach is going schitzo. Occasionally, it works fine, but most of the time it goes to around 4k rpm immediately upon startup. The needle moves slightly as the engine revs, but not more than 4-6 hundred rpm. When you turn off the ignition, it goes back to zero. Any ideas?

Anybody?

Buy an autometer!!;)