i have a 94 buick skylark with a 3100 engine it won't shift by itself i traced the vacume line down to the vacume module and have full vacume down to the little check valve what does that check valve do and is it nessasary also my cruise doesn't work anymore do they come off the same line or is there a resavior somewhere to look for it would be nice to have a complete vacume diagram the one on the car doesn't go into details,any help would be most appreated.

Can you take a photo of the check valve and post it, that would help identify it.
Do you have a sticker under the hood that shows the emission components?