I've been trying to hunt down a vacuum leak for a while now (Vents work on dash only) I'm curious if there is suppose to be a third vacuum line connected here, on the very back port. This is the vacuum canister next to the coolant reservoir on my 97.

 

check this thread out..
https://www.cherokeeforum.com/f2/fro...er-what-45351/

 

I think that is the fuel system charcoal canister, not the vacuum reservoir. And yes there should be hoses on all of them, however I don't think that it is the source of your vacuum leak. You can put your finger over the open fitting and see if your idle changes!

 

Hmmm. Does anyone else know if this is the case. It looks like it has vaccum lines running into it. This is not the one in the bumper it us located to the left of the engine next to the coolant resivor

 

4jeepers is correct, thats the Charcoal Cannister.

The vacuum cannister your looking for is inside the front bumper on passenger side.

Check the lines that come from here..

 

ya like it says on the thread link i posted. look in your bumper on the passenger side for the canister and there will be lines coming out of there check those. If they are plugged in and look good then move your battery and the lines run by it. Check them because sometimes they get cut. That happened to mine.