2002 Corolla - high idle, no CEL

[93corolla5speed]

Just bought this car today, 2002 Corolla with a 4 speed automatic, 100K miles. When I start it up cold, the idle is fine...where you would expect to be on a cold start. Once thoroughly warmed up, the idle is way too high, as high or higher than you would expect on a cold (winter) start. I don't have a tach, but I would guess its cranking 1300-1500 rpms.
There is no check engine light on. Yes, the light is operative, as it comes on with the key in the ON position before starting.

I looked under the hood, and no surprise, there is no idle adjustment.

What is wrong here???

I can take it back to the dealer but I don't want to if it is an easy fix...

[moviestar]

air conditioning on? when i have my ac it idles around 1200...

[93corolla5speed]

No, it's high with the A/C off. Turning the A/C on will decrease the rpms a little with the extra load on the engine.

I know what you are saying about the A/C keeping the idle high when its engaged...nothing to do with this particular idle problem.

I have been reading through the forum after searching for 'high idle' and I keep seeing people suggesting that cleaning the throttle body is the answer. That would make sense, since a dirty intake would raise the idle without triggering the check engine light. I will have to get some spray and hose it out tomorrow or the next day, and see if that helps.

Do you think that is a good idea?