That was years ago when Chrysler didn’t have the manufacturing capacity to build enough V6 engines and relied on Mitsubishi for engines. The 3.0 L engine had a problem with dropping valve guides, when this happens the valve seal pops off.
The field fix was to move the valve guild back into position, cut a grove on the outside of the guide and install a snap ring to prevent it from dropping again. The problem was supposed to have been corrected for the 1992 production vehicles.