ok so im soon to buy a 91 prelude si 5 spd b20a and the idle idles bewteen 1.5k and 2k is that the idle/air control valve??

 

Probably a vacuum leak.

 

ok thanks ill have to check that

 

+1

It COULD be the IACV but if it's consistently idling at that range, I would definitely suggest vacuum leak. Just check all your rubber vacuum hoses (that car is old and most likely so are the lines) as well as your throttle body gasket, and intake manifold gasket too.

 

the motor was just recently swapped