The OE valve springs are subject to breakage, bending or fatigue failure. Broken portions of the spring can cause the associated valve to stick in either the fully applied or released position. A fatigued spring will not have enough force to fully stroke the valve to the released position. Complaints vary depending upon specific location, but can be seen in the chart. The Sonnax springs will restore proper function to the associated valve when replacing a broken, bent or fatigued spring.