The blend doors are moved by electric motors on a 1998 Voyager. Vacuum is not used.
You can find a vacuum line diagram for a 1993 Plymouth Voyager in the owner's manual. You can also find it at various auto stores.
No vacuum change at the MAP sensor.
check for unhooked vacuum lines
You can purchase a repair manual at most Auto Parts stores that should have a diagram. Also look closely on the underside of the hood.
could be a vacuum leak
Check the vacuum lines on the driver side of the engine.
find the vacume line and check for a leak in the system
Posible dirty throtle body or defective idle air control motor(located on TB).
They start at the vacuum pump on the driver side of the engine, go up to the firewall, across to the pass side, and then inside the dash at the ac line area.
as it says here http://en.allexperts.com/q/Chrysler-Repair-807/cruise-control-dodge-neon.htm you could check the vacuum cable. I have the same problem on the same car.
I believe it is only ounces, not pounds. If you buy the recharge cans with the gauge on them, they will get you in the ball park. You should checks for leaks first by using a vacuum pump to remove the air (and contaminants) before adding freon.
On the 4 cylinder engine it is screwed to and part of the throttle body injection unit. The 3.0 litre V6 it is attached to the end of one fuel rail and has a vacuum line and a fuel line attached to it The 3.3 litre V6 it is a little brass coloured pot with a vacuum line attached clamped into the fuel rail.