Waynerd

96-99 4.0 heads used the lighter spring rate valve springs and they are prone to weakening. Cylinder one in my 98 4.0 has nearly identical compression to the other cylinders but a leak down concluded that a valve is either not closing or seating completely. Very possibly due to a weak valve spring. Haven't pulled the head yet but it mostly affects my idle and it's burning pretty good with no gas in oil.