David, >From your description it sounds like the idle speed motor is frozen. Even though the motor may admit a hum sound it may not be operating. The easiest way to test the motor is to completely remove it from its mounting, repeat the test that you performed previously while looking through the aperture at the bottom of the unit. If the crescent shaped valve does not move than the motor is bad or it may not be getting voltage from the idle speed ECU. There are no vacuum lines associated with the idle speed circuit. "We're here to help you" Seasons Greetings! DMC Help / De Lorean Services / <dmchelp@xxxx> Web Site: (TEMPORARY)<www.geocities.com/dmcjoe>