idle going crazy!!!

Hey everyone,

My name is steven and i have a 2003 honda accord i4 coupe and it is completely stock with 130,000 miles on it, and i've just recently last month had the valve head done since the aluminum got really messed up due to driving my car while it was overheating and so my car lost compression and one day it wouldnt start but now that all that is fixed and my engine is put back together and my car starts perfectly, my problem now is that when i have the car on park and its on idle the cars RPMs go up and down on its own between 1,500-2,500 RPMs i checked to make sure that the intake manifold and my throttle body was put on fine by the mechanic, i also check the air filter and it is also good. I've been doing my research on what it could be and ive learned that it could either be the IACV or i may have air in the system but i highly doubt it since it's not revving randomly but it revs up and down with the same rythem so im thinking the IACV which i will check it out tomorrow. (and no i dont have my foot on the pedal -____-) but can anyone give me any suggestions or has anyone had the same problem? and i looked through this whole forum for maybe any related problems but i cant find nothing.

NOTE: I took apart the engine once when i was going to have the valve head sent to the shop and done since i messed it up due to driving while the car was overheating, and i took the engine apart without any experience or supervision so i took out alot of parts i shouldnt have so that may have something to do with it. (may be something loose??)