Well, I have owned this 97 SE 2.5 stick for 2 weeks and getting it fixed up. Owner neglected it for YEARS. But it was cheap and ran. Owner said it needed a tune up. Well I put in new copper plugs, wires, cap and rotor and cleaned out the IAC. Every time I start it cold, or has been sitting for more than 15 minutes, after 1-1.5 minutes of running it starts to run ruff. If sitting it will spit and sputter, but never die. I can rev it up but its missing will last almost a minute. If I am driving and it does it, it feels like someone shut the Jeep off. Put the gas peddle to the floor and it will run, but backfire thought the intake a few times. Beat on it for 15 seconds and it will run fine. From then on, it will run for hours and not give any problems. There is no stored codes and no check engine light. I am guessing the upstream O2 sensor is bad and not warming up quick enough?? Computer switching from open loop to closed loop and sensor not reading right? Why not setting a code??? Your ideas?
PS. I normally drive a 97 Sport 4.0 auto and I now can say, the 2.5 is a dog compared to the 4.0!!!