idlen still bad

If it is a vacuum leak automotive shops seal the intake at the throttle butterfly and remove a vacuum hose going to the engine. We use a machine made by Vacutech, but Snap on, Matco and other manufacturers make a tool that generates inert smoke at about one and a half to two pounds pressure. When this smoke is placed in the vacuum hose taken off the engine the smoke then escapes through the failed gasket, or vacuum hose that is causing the vacuum leak and rough running. Everyone has their own method for finding leaks, water in an oil can, oil in a squirt can, propane and Chemtool can all be used, (Chemtool being the least safe). When, the oil, propane or Chemtool comes in contact with the source of the leak the idle speed picks up that area is where the vacuum leak is occurring.