I recently picked up a 1994 mustang for my son. I am trying to turn the idle up a bit. It runs around 500-600 now, seems low and its a standard so he is having a hard time starting out. When I turn the set screw under the hood by the accelerator pedal the rpms do go up but jump right to 1000-1100. I cannot seem to get it in the middle where I want like 800-900. But even when I do set it high within a short time the rpms settle back down to 500-600 region. Is there another way to set the idle up that I am missing. Thanks.