My recently purchased used 2000 CRV had a valve timing adjustment at 97000km and is now a 160,000km. How can i be sure that it does or doesn't require an adjustment again now? Should I do it anyway just to know its been done? Also, on of the spark plug ports (deep on this model) has some oil build up (not pooling yet). Should I have the valve cover gasket immediatly or wait until its worse? Would the gasket get changed anyway with a valve timing adjust?