my girlfriends 92 gs is acting weird... whenever you turn on the ac the rpms will jump up from idle to about 1500 rpms and the car will lurch forward if its in drive... she has to hold the brake pedal down really hard to keep it from moving when shes stopped... sometimes it will only do this once and sometimes it does this continually like a vacuum leak would... if the ac is off the car runs fine... anyone have any ideas??

 

anyone????