Saab: 1986 saab 900 turbo, vacuum leak, rubber gaskets

Question
my saab recently started idling rough.the idle is up and down when it is cold.. after it warms up,RPMs drop fast when shifting.feels like there is a vacuum leak but i can't see to find anything.any recomendations? thanks,caseyjones

Answer
Casey:
It certainly sounds like a vacuum leak. The easiest way to check for one is to pinch off the several vacuum lines leading from the intake manifold, one at a time. In practice the most common spot is the thin black hose leading to the cockpit which controls the heating duct doorways...it often cracks at the intake manifold nylon vent plug.  Also, the rubber gaskets sometimes fail.  A good test is to spray carb cleaner (or starting ether) in the vicinity of a suspected leak and if the engine speeds up  or otherwise "changes", then that is the site of a leak. This test is especially useful if a leak is suspected at the gasket between manifold and head.

          Hope this helps,

                              Jerry