Backfire

My '98 4.0 has 213k on it and the other day I started the engine and the jeep started shaking like crazy. Eventually the engine quit and refused to turn over so I looked under the hood and quickly discovered the problem, a deteriorated rubber elbow on the left manifold. The elbow connects to a threaded breather type valve in the manifold and has a thin piece of black plastic routing to the purge solenoid next to the left fender/air box. When I removed the rubber elbow from the manifold the engine eventually turned over and idled fine, I then headed to autozone and found replacements of the same diameter, I cut them down a bit to match the length of the originals. Since its been a while I changed the plugs and wires, coil pack along with cap and rotor while I was at it. I replaced one plug and wire at a time to ensure I didn't mix things up, same goes for the cap. Now the jeep seems to take a few more seconds to get started but once it does it idles fine.

Now when I hit the gas hard the jeep will hesitate and then backfire. If I'm smooth on the gas the jeep drives good, whether city or highway. When coming to a stop the jeep will sometimes buck slightly like it wants to cut but doesn't. The backfire sounds like its coming from the air box and oddly enough, my aftermarket radio no longer plays in the accessory position, probably a separate issue. So far there's been no check engine light.

I really need to keep this jeep for a few more months and I would hate to put big money into at this stage. Any ideas?

Have you tried the key on/off thing yet?
Without starting the engine.....key on, key off, key on, hey off & end with key on......there may be a stored code where your odometer would be.

I haven't tried that but I have an obd2 scanner which I've hooked up numerous times since this problem began. Two days ago I was out and about and something told me to try a new TPS so I headed to autozone. As I prepared to leave the autozone parking lot the jeep refused to start so I cleaned the throttle body and installed the TPS on the spot. This got me home but the idle still seemed off as it felt as if it would cut off when switching gears. The following day the jeep refused to start once again at the autozone lot so I installed a new IAC on the spot. I'm a bit more confident its not going to cut off on me now but the rpms still drop when switching gears, giving the feeling it wants to shut off without doing so.

A few days ago I also noticed a clanking sound in the rear when hitting bumps, when stopped in traffic I could also hear this sound. My cat had came loose from the pipe going to the rear causing the muffler pipe to bang against a suspension part. I had this replaced/fixed this morning but I still have backfiring under the hood when hitting the gas hard. When I parked I disconnected the neg batt cable in hopes the ecm resets clearing the problem. Its a long shot but hey.

Heres my update for anyone interested. Problem turned out to be a bad fuel pump, i found a shop that tested the pressure which was on the low side so i changed the pump and shes back to normal. Ive changed the pump in the past but only because i was getting erroneous fuel level readings. After chasing parts i changed just about all sensors minus the cam and crankshaft sensor and with everything else i did I'd say it's pretty tuned up, hopefully i get another 100k out of her.