So i own a 2 door 1999 civic ex.
I just put a new engine from 2000 4 door civic ex
both automatic
only difference would be the 2000 4 door ex had abs and mine doesn't but i dont think that would be a problem.

everything works perfect. car turns on and no check engine or anything like that.
is just that the RPM's doesn't work. it worked once but then it just quit.

i was thinking it was a sensor or something i left unplug. I just really dont know where or what to look for. If someone can help me out it be great.

 

The tachometer of your OBD2b Civic gets the rpm signal from the blue wire that runs from the gauge cluster to pin A19 of the ECU. Check that wire for an open or short.

 

You can also jump it from the ecu, to the cluster just to make it work till you find the short.

 

can someone please be a little bit more detailed please