Unfortunately,DC/JEEP decided that small little plastic lines would supply the vacumn needed on the CHEROKEE.
Unfortunately,those small plastic lines will deterioate due to heat/cold as in expansion/contraction and so on.....
There should be a vacumn cannister behind the front bumper,on the passenger side.Starting there,trace ALL the lines throughout the engine compartment.These lines are usually black in color and can become very brittle.Any broken lines can be spliced with 5/32" gasline hose,and will fit very tight with NO NEED for clamps.
Some of these lines will go into the firewall where they may have rubbed against the body and have developed a leak.
One leak will affect the whole vacumn system(DC is so smart
)
Some of the lines run UNDER the battery so you may need to pull the battery to check those.....
If the vacumn cannister itself is broken or damaged then you may need to replace it or search some forumns for options on replacing
