1990 Nissan Sentra Fast idle speed problems

Too fast an idle speed and refuses to come down to a normal idle speed despite your best efforts to back off the air bypass adjustment screw (fuel injection), air is getting past the throttle somewhere. Common leak paths include throttle body gaskets, intake manifold gaskets, and of course, any of the engine's vacuum fittings, hoses and accessories. It is even possible that leaky O-rings around the fuel injectors are allowing air to leak past the seals. Another overlooked item can be a worn throttle shaft.