what is this?

Alright so my jeep wouldnt start and I thought it was the cps, but I've always had this ticking coming from under the dash. I found it to be this box thing. its right by the ash tray with a big plug going into it. I googled the part number and found a bunch for sale but no info on it. anyways I unplugged my battery and unplugged this box than plugged it back in and bam, starts up and idles, runs perfect and no more ticking. what the hell is this? heres a few pics.

Could it be the blower motor relay? It's been a long time since I had an 87, but I don't remember many other relays down there. Your best bet might be to unplug it again, and then see what doesn't work with it gone.

why would it stop my jeep from running? It runs perfectly fine now and with it un plugged

its not the heated glass one. this has 5 plugs not 4

Unplugging and replugging the battery may be the key here. Are all of your terminals (+ and -) tight and shiny clean?

I suspect Pelican is right, and that the relay clicking was a symptom of low voltage. It may also be that when you unplugged the relay you disturbed some poor connection under the dash - a bad ground or something, which might also influence the ECU, which is not far from where you were working. If the problem returns, I'd check down there again and see if wiggling wires and connections has any effect.

I repeat that it's been a long time since I had an 87, but it had wiring even more minimal than some of the later ones, and one thing I remember is that a few things were grounded in common with the cigarette lighter, not very clever.

And that now reminds me, since XJ grounds can be so troublesome, to remember to check the ground strap between the firewall and the valve cover. It's a braided strap which corrodes easily, but not always visibly until you touch it and it crumbles to dust. That can influence many things.

I checked all the grounds etc. still wanna know what that box is. it runs without it...

Note from DJ
What color wires are going to the plug of your mystery item from left to right on your second photo?