I just bought a 97 Wrangler with 142,000 on it. It is the 4 Cyl 2.5. It has been running very rough lately, spitting and sputtering seeming like a fuel issue. However when the engine cuts and spits, the rpm gauge shoots up, but there isn't an increase in the rpms, or no audible racing of the engine. The gauge shooting up is very quick like within a second then it comes back to normal. I am wondering if this could be the oxygen sensors? I should say that there sounds as if there is an exhaust leak up high near the engine. Also the other day the muffler sound much louder than normal and the spitting and sputtering was terrible, so I climbed underneath to find the tail pipe had disconnected from the muffler, once hooked back up the spitting and sputtering was far less and got better, but is still there. Any ideas would be helpful! Thank you.