I say you're looking for a vacuum leak. Follow the supply line that goes to the control panel. Make sure there is good vacuum there. If there isn't, trace it under the dash, through the firewall, and to the engine (source). My guess is you will find a broken hose near the firewall.
Let me know what you find. Also, if the engine is running, you may get lucky and hear a hissing sound from the leak.
Wednesday, November 18th, 2009 AT 9:29 PM