alright i have a 89 sentra that has been very well taken care of and all of a sudden it idles very high! ive tried a couple things like checking the throttle cable, trying to adjust the screws, etc. but nothing yet! someone please help!
I had this happen to me once. There is a wax type high idle device that is activated by the coolant temperature. The plunger extends out when the coolant is cool and gives you the cold fast idle. When the engine reaches operating temperature the hot coolant flows through it and retracts the plunger to allows the idle speed to drop to normal [when warmed up]. I'd say your fast idle plunger is either stuck in the cold position or you have an airbound cooling system and hot water cannot get through the fast idle valve to retract it. Pull the rubber hose off of it and blow compressed air through it to make sure it's not clogged and then bleed the cooling system properly and the warm idle should return to normal.
If what I just explained makes no sense to you, print this reply off and give it to your local auto technician and ask him to fix it for you.