If vtec cuts out or malfunctions, check your plug connections before you disassemble the entire car. In other words, do the exact opposite of what I just did today.
Seriously though – the vtec solenoid is often a place where oil may leak slowly at it’s mounting point. And overtime, that oil/grease/grit can work its way into the vtec pressure switch (usually a green plug). If that happens, it can & will lose conductivity. To remedy: just spray some brake/carb cleaner into the plug, and you should be good as new.
That’s what had happened to my CRX today. My solenoid was leaking a minimal amount. I was already changing the oil, so I figured I’d just put another solenoid on it. I did, and vtec didn’t work. So I scratched my head, and swapped it back to the original solenoid. Vtec still didn’t work. Frustration & confusion built… I was tearing into things, and I was overlooking the obvious. But – when I had disconnected the plugs, juuuuuust enough oil must have gotten in the plug to cause a problem. Lesson learned. Thanks to Sean Bradford & Joe Backyard Schneider for letting me ‘phone a friend’.