Injector or something else?

Okay so i have a 2kd which is the 2.5ltr, very occaisonally maybe once a week, when im sitting in traffic it will suddenly start idling high, like just on 1k rpm, rather then the usuall 750ish. What are the chances this is an injector issue? I dont blow any smoke, im on 340k km and only just started to get a small amount of oil circling into the intake, i dont believe i have any piston knock.