been there many years ago with the 1986 4wd 2.6....don't remember how many were broken, had to replace all "adjusters" & "rocker arms". first symptoms were engine tapping, cold running, poor starting (cold), gas in oil, clogged catalytics. make sure to soak all new parts in oil (overnight if possible) prior to assembly & recheck torque after break-in (14-15ftlbs rocker arm "c" & 15-19ftlbs rocker arm "a"). why it happened...only thing i could come up with is "adjusters" wore/got stuck...never happened again. best of luck!