So i fired up my crx for the first time , it has the b18 swap in it and it idles around 3000-4000 rpm. what could be the problem?

 

are you getting any codes?? ur throttle cable could be to short or ur throttle cable bracket wont let it adjust to lower the idle anymore. could also be iacv

 

BIG vacume leak
same thing happened to me, my problem was that i was missing a part on the intake manifold,
not sure what its called but its under the throttle body, it has 2 coolant lines going into it from the head,
if you are missing it there will be 2 holes where the air is comming in causing the high idle,
ill try and find a pic of it

 

check the vacuum hoses first. pretty sure its something simple

 

check intake manifold gasket, i had the same problem on my d16