When I stat my Maxima and start driving the tachometer works for about 2 minutes. After the 2 minutes are gone the tachometer reads about 2000 RPM off. The only way I can test this is to redline the beast and determine how far off it is.

I know that this is not normal so if any of you have had this occur before or have an idea of what is causing this, it would be greatly appreciated.

Thanks!