I had the same problem a week ago. The vacuum line on the drivers side next to the master cylinder is probably broken where it disconnects. Do a search a you will be able to find some pictures of where you need to look.
What they said.....Look for a really thin vacuum hose on the pass side fire wall next to the heater hoses. Follow it towards the vacuum tree in front of the driver's side. It has a plastic connector somewhere behind the upper intake. It is probably cracked there. Use duct tape for now to seal it..then try...That will buy you time to get a new hose..
RC
Hey vernell69 I see you live in glendale. That's cool. I live in Gilbert. You should check out 1320stangs sometime there is a lot of az guys that get together over there.