I have a 1994 Mercury Topaz and this is what it is doing: runs fine when in drive but when in park it idles up and down (way down). After a few times of doing this it dies. I tried to start it again and it wouldn't start. The battery light came on. A few days ago my dad checked my vacuum hose and the end of it was really cracked so he cut off the end and reattached the hose. If there is still a leak in the hose could that be the cause of the up and down idling and then dying?

Yes, Little Bill, vacuum leaks typically cause the rpm to fluctuate. To me, it sounds like you need to:

. Remove and fully charge the battery. Most auto parts stores will test and charge batteries for free.

. Clean battery terminals and cable connections.

. Replace the platinum spark plugs with the exact Motorcraft plugs that came in the car. Stay away from cross-reference plugs.

. Clean the Idle Air Control Valve (IACV), throttle plate, and throttle body:

https://www.askmehelpdesk.com/cars-t...ml#post1054149

. Remove air filter, clean and wipe down the air box with a damp rag, allow it to dry, and install a new air filter.

. Increase idle rpm, if necessary, by adjusting the throttle cable. This should prevent the battery light from coming on, in conjunction with a fully charged or new battery.

. Replace fuel filter:

https://www.askmehelpdesk.com/cars-t...ml#post1389619

You have multiple vacuum lines; anyone of them could be the problem, especially considering that you already found one that was dry-rotted.

The battery light coming on when it stalls out is normal; most people don't realize that because their cars usually don't stall out.