High idleing

Too fast an idle speed.

If an engine with computerized idle speed control is idling too fast and refuses to come down to a normal idle speed despite your best efforts to in adjusting air bypass adjustment screw. Air is getting past the throttle somewhere. Common leak paths include the 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

Could also be the idle speed control and throttle speed sensor-