Oh man, sounds all too familiar. If you have oil in the lines you have or did have a bad Vac shut off switch. Lots of threads on this. If it is shutting off OK, someone may have replaced it but never cleaned the lines out
or it may be starting to go bad, but still provides enough vacuum to shut off the engine. You should take them off and clean with brake cleaner or equivilent. Should unplug and clean at the keyswitch as well. You don't want all that oil around in there. You can unplug at the valve by the ignition and run the cleaner from the other end of the lines in the engine compartment. Catch the runoff in something or you will have stained carpets. Ask me how I know this
As for the shifting, that is good news it shifts well when you isolate some lines, that means you don't have to mess with trying to adjust the Tranny at all. You need to figure out where your leak(s) is coming form. Many threads on this as well - good to have a vac gauge and a Mity Vac. Mine was from the line going to the HVAC control behind the dash - I just plugged that line off and plugged where it "T" off from, no more Vac leak. I didn't need that center diaphram to work anyway. Have fun
