Cadillac Repair: cadillac idle, vacuum leak, vacuum lines

Question
I am trying to get an emissions test done and yesterday when we pulled up there they said they need a max idle of 1100 to run the test and that my car is higher. How do I adjust the idle down? can I do it manually like the older cars. I have a 1985 deville.

Answer
NO, Do NOT try and adjust ANYTHING. The most likely fault is a vacuum leak in one of the vacuum lines, a faulty or mis-adjusted THROTTLE POSITIONING SWITCH or a faulty IDLE SPEED CONTROL motor or a buildup of a blackish residue on both side of the throttle plate and surrounding area within the throttle body that needs to be cleaned off.