Every time I engage the clutch my rpm goes almost dead and then to idle and sometimes my car shut down. Today I took off the vacuum line attached to the pressure regulator and the car is not doing the low rpm anymore. Can anybody help me by telling what is wrong, cause I'm stock on that, I don't know what else to do to fix that rpm problem.

 

i have had the same problem as well...but did not disconnect anything....it almost seems like after i hit vtec a couple of times it doesnt do it anymore......but yeah i have heard many others had the same problem

 

Idle fluctuation (and even stalling) is normal even on stock S2000s, especially if the weather changes much.

 

Don't you mean "dis" engage your clutch

 

Pulling the vacuum line off the regulator introduced unmetered air into the intake, and increased the idle speed. This is a vacuum leak, and need to be reversed.