you are correct the iac can do this but also try this disconnect the battery and turn on headlights then connect battery again , do this in morning before you start car then crank over engine dont give it any accelerater let it relearn idle,
it will race up rpms then settle back to where it should be ,
sometimes the car just needs to relearn its idle when its cold . a symtom of the .
computers back up battery "memory" going bad
Well. i went to my mechanic and he put a Scanner and he got a code. I think was the MAP/MAF low than expected or some like that.
So, he cleaned the MAF and cleared the code and i went to race a little the car again, pushing some boost and after, i come back to the mechanic. Again, he put the scanner and he didnt found anything.. I left the car with the engine on about some mins. and after, the car began to shake. He check on the scanner about code and no code was there!! .
So, he made a "controlated error test" or some like that and i got again problems with the MAF. So, it will changed. Today, im going for my car and test it..