1992 Toyota Pickup number 2 cylinder not firing

When I start the truck in the morning all cylinders are firing but when the motor heats up the #2 cylinder is not firing I have changed all spark plugs and cables for spark plugs rotor and cap also the coil this did not help I pull the # 2 spark plug wire off and its not firing Im thinking a valve ajustment or a sticking valve can you recomend and thang before the money hungry mechanics eat my money $