Valve lash adjustment determines how far the valves enter the cylinder and how long they stay open and/or closed.
While all valve adjustments must be made as accurately as possible, it is better to have the valve adjustment slightly loose than slightly tight, as a burned valve may result from overly tight adjustments.
Most of the engines covered by this manual (with the exception of the 1.9L gasoline and the 2.2L diesel) utilize hydraulic valve lifters. The purpose of hydraulic lifters is to automatically maintain zero valve lash, therefore no periodic adjustments are required on engines equipped with them. However, most of the vehicles utilize rocker arms which are retained by adjusting nuts. If the rocker arms and nuts are loosened or removed, they must be properly adjusted upon installation in order for the lifters to work.