98 SL2 1.9 DOHC REALLY high idle at startup

Idles really high at startup until the engine gets to normal operating temperature and falls back to normal. Takes 10-15 minutes. I recently de-greased the engine and think I may have fouled a sensor...though the check engine light is NOT on. Any ideas would be greatly appreciated. I'm afraid if I keep this the way it is it will cause damage to the engine.

Check all sensor connections for looseness and moisture contamination first.

Step 1 is generally, pull OBD-II codes. Yes, there can still be codes stored yet the dash light not activated.

Check for vacuum leaks.

The Idle Air Control solenoid could have problems retracting due to carbon build-up or/and is failing. It may be that it's opening up okay to allow for cold idle, but is having difficulty closing off as the engine is warming.

Let us know what happens.