Does the 2.5 have a crank position sensor? My 89 4.0 XJ would act up like that, and found that if I unplugged and reconnected the sensor connector it would run good for a couple of months then start doing it again. Disconnect and reconnect and it was good again. Finally cut out the connector and hardwired it, no issues ever again. Don't know if this is your problem ,but worth a try.