there is a filter!!!! its called the spool valve.. take off the vtec solonoid and its like a gasket/filter looks like a fine net. clean with brakeclean. the filter filters out any debris. if the filter clogs the spool valve will drop oil press to the rocker arms and vtec will not turn on or turn on on some cylinders and not all. also the filter keeps out debris so the timing piston(the little rod that connects all the rockers to the deep cam lobe) wont stick. if its not clean it would throw a check engine light. (p1259 dtc) i know because im a honda tech. and had a shitty experince with that on an accord.