2 nights ago, my rpm gauge shows that it idle at zero, the needle is right on the resting pin, but it didn't shut off. The car its idling right, and the heat meter show that my car overheats even with the fan on. Last night I swapped my clusters assembly with a friend(his car been sitting),with his cluster gauge, my car idles fine, it didn't over heat. Heat meter would go up to half way, then fan kick in, drops back down to normal like 1/4, but still go a little over half if i am going like 85mph+ on the highway for 5 minutes or longer. So I figured everything back to normal. Tonight I was driving the car home, realized that the rpm gauge its not reading right, when i get on the gas, every once in a while the rpm gauge would go up real fast, then drop back down to where the rpm should be.

Anyone have any idea what's wrong with it?
what other wires should i check besides the ground wires?
maybe distributor?
its a 92 B16a in a 92 EG w/ stock radiator.

 

is this on the stock meter? and also how old is your battery? because when my batt was not grounded properly it would not take a charge and was screwing with my autometer tach and my stock tach. But since you said you were driving at night I'm sure you would have noticed that your lights were dimming so maybe that was a bad idea. What I would try is hooking up a aftermarket tach if you or one of your friends have one and see what that reads if it reads ok then start to check your wiring.