sure we love variable valve timing and lift electronic control (vtec). but vtec requires maintenance just like any other component or system in a car, and this little article is just one step out of many that can be done to ensure that your vtec is operating optimally and efficiently.
the vtec solenoid (spool valve) consists of two main parts/sending units. and inside each part, there is a gasket/filter that acts as an oil sealant to prevent oil from leaking and to filter out any contaminants or particles that can be present in the oil from lodging inside the main cavities and disrupting the vtec system. any blockage of the filters could certainly cause vtec to not engage, or, even engage inconsistently or sporadically, since vtec is mostly an oil pressure controlled system.
these are the two parts you will need for this project, technically called spool valve filters:
please note this little maintenance procedure should be done when doing an oil change or if you have all the oil drained out. otherwise, the oil in the head will drain out all over your block and tranny.
first step is to locate the whole vtec solenoid. it is the little brownish cylindrical part next to the distributor, and the part below it that it is bolted onto–it covers the cam end plug as well. disconnect both sensors, as seen below. the green sensor is the oil pressure switch, and the other one that is already unplugged is the actual spool valve.
using a 10mm socket, remove the 3 bolts that hold the whole solenoid to the head. remove the solenoid. be sure to have a shop towel underneath the solenoid as leftover oil will be sure to ooze out. here is the whole solenoid removed:
replace the filter. my original filter’s gasket fell apart and was no longer pliable while trying to remove it. looked like it was nearing the end of its service life and was susceptible to future leakage.
using a 10mm socket, remove the other three bolts that hold the upper portion of the solenoid, then replace the filter.
then, reassemble and replug everything back up. important things to note while reassembling are:
- lube the new gasket/filter parts with a light dabbing of oil, in the same manner you would the gasket of a new oil filter. this will give it a good seal and prevent unwanted leakage.
- always torque down all the 10mm bolts to spec–9 lb-ft.
mods, please move this thread/article to the appropriate forum, if applicable. i just wanted to give some of the vtec lovers some heads up and some easy ways to keep their vtec running healthy and happy. comments, questions, additions, corrections (or $ donations) welcomed. 
Good article 
