If you have not done this recently, or even at all on your Cherokee, you should do this at your earliest convenience. On both sides of your engine are your engine mounts. I'm not talking about the rubber mounts, I'm talking about the metal fork that attaches to the block and bolts to the rubber mount. Each mount has three bolts holding it to the block, and over time these bolts can loosen. All it takes is for one bolt to loosen, and the other two will bear the brunt of the engine's weight. This will eventually lead to sheared bolts.

At the very least, get underneath your vehicle and retorque these bolts to the factory-specified 45 lb.-ft. of torque, or replace them with matching grade 8 bolts coated with Loctite (the bolts from the factory are only comparable to a grade 5).

I was unaware of this issue with the engine mount bolts, and didn't bother to check them. Every single bolt on the passenger side of my engine sheared off and was left in the block, and the three on the driver's side were incredibly loose. It was a long, hard process to get the engine back into place, replace the bolts and get everything back together, and well worth avoiding with 20 minutes worth of work.

 

This is a known issue, and I've covered it before.

It's not so much that the screws loosen, it's that the holes weren't drilled and tapped to a sufficient depth. Therefore, the screw bottoms out against the bottom of the hole, instead of the underside of the head.

This results in a failure to provide the tensile preload that the screw requires, which leads to screw failure in shear.

After you torque your screws, take a small (.003" or so) feeler gage and try to slip it under the screw head. If it goes under even just a little bit - back the screw out and put a 3/8" flat washer on the screw. Then reinstall (a bit of LocTite 242 won't go amiss, either.) This will prevent the screw from bottoming out in the hole, and have it bear against the underside of the head (which is what's supposed to happen.)

 

Been there, done that. I snapped mine off. Had to drop the cross member, remove the other side motor mount, and drop the engine down until it was basically sitting on the front diff. to get to where I could easy out the bolts out.

 

I got around the issue of the screws bottoming out simply by the fact that the grade 8 bolts I purchased at the hardware store were about 3/32" shorter than the stock ones, so they're keeping that mount pressed tightly against the block.