Check the fuel pressure regulator
If the engine is idling high after it warms up it could be a vacuum leak somewhere. If the PCM detects a lean fuel mixture, it will add a little throttle to compensate. Could also be a bad or dirty IAC. Try cleaning the throttle body and IAC with throttle body cleaner first. Do not use carb cleaner. A malfunctioning IAC will not necessarily throw a code light, but it could throw an internal code which will not illuminate the bulb on the dash. Have it checked anyway.
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