I have an b16 head on a gsr block and it is in a 94 civic hatch cx with the cx wiring harness. When I turn my car on it revs up to about 2500-3000 and stays there for a few minutes but then eventually it drops to around 1000. I think this problem has something to do with the cx harness and the b series iacv but I wasn't able to find a definitive answer. Can someone please help me out?

 

its normal for the motor to idle high while the engine warms up, watch the temp gauge, i bet ya the rpms will drop when its about half way up.

 

2500-3000 is a bit excessive tho for cold idle..it should be 1500ish ...clean ur IACV? inside the intake manifold? Butterfly of TB not geting stuck? loosen ur TB cable? TPS sensor set to right voltage?

 

could be TPS.. mine goes as high as 3k sometimes