Actually vtec doesn't kick in until the engine is at normal operating temp so if your coolant sensor isn't working then the ecu will probably beleive the car is constantly running cold and not at normal operating temp. Trust me my friends crx with a b16 had this problem. His temp guage read cold all the time and his vtec wasn't working and he replaced the coolant sensor and car started to run at normal temps and vtec was working again.

And Vtec doesn't kick in when the car is in neutral so how would him revving in the driveway help??