One problem related to gas recirculation valve (egr valve) has been reported for the 1998 Jeep Cherokee. The most recently reported issues are listed below.
Belt pulley disintegrated after 2600 miles on new vehicle. Fragment of pulley was ejected at sufficient velocity to puncture hood leaving approx. 1/2 inch hole. At approx. 65 mph the engine rpm was only approx. 2500. It is possible that this failure could occur in a standing vehicle, causing a hazard to others.