hey... i just got a b16a2 swap done last week into a 96 civic cx.. also i had a new o2 sensor (before cat) put int... the one after cat is old... and when the car is rolling in neutral the rpm is at 1500... when it's at a stop light the rpm is at 1300, after a few seconds it drops down to 800-900... has anyone had this problem? i am using a ractive tach gauge cause the cx never came with a tach... i extend the tach wire to the ecu's wire for the tachometer. is that the problem? forgot to mention.. it wasn't doing that when i first had my tach hooked up 2 days ago... it started doing that all of a sudden...

 

Vacuum or maybe your throttle cable is too tight

 

maby im just being a smarta$$ but maby you should have did what i did for my cx and just put in a ex gauge cluster so you have a factory tach