97 grand cherokee 4.0

Welcome to the forums !

Do you have a cel lit up ? if so pull the code(s) and post them as this will help us diagnose the prob. even if the cel is not lit up you should still check for any codes. as for stalling I would do a fuel pressure test – key on engine off and with engine running. when it dies I would test for missing spark. keep us posted.

You might want to go to another place and have them check it for code(s) and pending code(s) if there still is not any then there might be a wiring problem to the CEL.
Does it not start right after it stalls?
If so check for fuel and spark when it does not start.

a while back – my ’99 Jeep Cherokee stumbled when idling and stalled at random times…the check engine light was never on and no codes were stored. after doing all my own troubleshooting and leaving it with my mechanic for a few days, we couldn’t figure out what was causing the issue. it even stumped my mechanic. since he didn

I’m surprised there wasn’t a code stored and that’s somewhat concerning as anytime the light comes on it should store a code for at least 50 starts of the vehicle or someone clears it. You might want to take it somewhere else to see if they can pull the code as that is your most important clue to what is happening, without that information you’ll have to goto the basics and find out what’s missing during the stall condition, fuel or spark, and that can be tricky in your situation, I’ve actually driven around with a fuel pressure gauge taped to the windshield waiting for a stall looking to see a drop in fuel pressure, it may come to this if you don’t find a stored code to get you started.

If your exhaust system is swollen up like a balloon, there’s got to be a reason for it. Check to see if the exhaust is restricted downstream from the muffler. Also, check to see if maybe it’s got a misfire somewhere in the system, causing combustion heat and pressure to enter the exhaust stream rather than pushing down a piston. You’ll need to replace the exhaust, make no mistake about it, but I’d want to find out what caused it to swell up before I replaced the exhaust system.

An easy test to see if the problem is a clogged cat is to remove the upstream O2 sensor and see if it runs better once everything gets warmed up. Granted, the local police may have some words for you about driving around with a hole in your exhaust, so you may want to keep the driving on public roads to a minimum. I’ve diagnosed a couple clogged cats over the years using this method, as it gives the exhaust some place to go rather than backing up inside the engine.

Sounds like you had a pretty big misfire or backfire at some point which could have damaged the cat and restricted the exhaust. I might remove an O2 sensor before the ‘blow up’ and take it for a drive to see if it works better, if it does this could indicate a restricted exhaust. That’s not all however, in order to have a ‘backfire’ on that scale there was probably a great deal of fuel in the exhaust which could indicate a rich condition, you might want to check your fuel pressure as well as check for a leaking injector or fuel psi regulator problem.