ok so i have a 96 civic ex manual....ok heres an idea on what the cars doing if im going down the road and down shift to pass someone at the point that vtec is supposed to kick in...vtec ingages but then it does a sputter and throws the code p1259....also the car has a light sputter when ideal (ing). so i did an oil change got spark plugs fuel filter and spark plug wires and also checked the screen in the solenoid...ok it still does the same thing its just not as frequent does any one have any other ideas....

 

you basically covered the most. change the solenoid and see if it still does it. oil pressure is the common cause of vtec non engagement.