Intermittent High Idle

[Ray Sta.Juana]

Hello fellow monkeys. My car has recently been idling around 1500rpms even
after it's been warm. Now at first I thought it may just need an idle
adjustment but it goes away and only comes every now and then. Most other
times it idles normaly (8-900rpms) Any ideas on why it's doing that? It's
not the throttle cable cuz I made sure that's properly adjusted and not too
tight. Is it possibly something that I just need to clean? Throttle body
maybe? Revving the engine has no effect and neither does shutting it off and
re-starting it. Only goes away with time and not with engine temp or any
other consistent factor I can notice. TIA for any replies

Ray S
98 Sentra SE w/mods