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Check coolant temp sensor. These fail often and cause all kinds of mystery problems. This unit acts much like a choke on old carb engines and can fail in different ways. Most common (I think) they fail such that the ECU thinks the engine is cold when it has begun to warm and thus the ECU delivers too long a pulse to the injectors so that the engine runs way too rich. I think it is also possible for the sensor to fail at any point between cold and warm such that the fuel mix is wrong except for the particular temp at which the sensor is stuck. Also O2 sensor has some fuel "trim" input.
check the MAP sensor (manifold absolute pressure). The ECM (car computer) uses that to keep idle at minimum 750 RPM. It's normal for it to run high when cold. These small 4 banger motors typically run hot, and they won't run right IF they're NOT running hot, ergo the idle is usually high when it is cold so as to cause it to warm up quicker. If the RPM's drop below 750, suspect the MAP sensor, &/or ECM.
Could be a dirty IAC (idle air control) and it's causing it to run high, also, could be a tstat going bad because it would make it run like it was cold all day...check your temp after driving for a while....see if it's lower than it should be.
Hondas are famous for this, my accord does it. This is normal UNLESS it still idles high after normal running temp. has occured. Watch your temp. gauge when it reaches normal temp tap the gas a little bit if the idle drops then it is fine