i have a 2000 civic ex with 156,000 miles. it will idle fine with the air off, but if the air is on at all, it has problems. when the air is turned on, the rpm's drop and it has trouble running. the rpm's will rev up and down, under 1000, and the motor sounds like it is about to stop. like it is not getting enough fuel or air. if i give it some gas, it will run ok for a few seconds and then it happens again. if i turn off the air, it stops and idles fine.

also, when the air is on, there is a hissing sound coming from the right passenger air vent sometimes. it doesnt happen all the time, but it is very noticible when it happens.

any suggestions on what is wrong or what i can do?