First of all, I have already searched for hours on this, so no need to sing that song to me.
For over the course of the past year or so I have had a bad idle during cold starts when the car is about half warm. It will start fine, begin its high idle, and then when the RPMs start to drop, the car will then begin to sputter and hunt for idle. I notice that the AFR will go from 14.7, drop to around 12 or so, then the RPMs drop and the car seems like it is about to die. But then the AFR goes lean at about 17:1 and the RPMs surge back up. This problem then stops after the car has warmed up completely and the idle is normal. I have only thrown 2 codes throughout the entire lifespan of this issue, and it was just the other night. As it was doing its thing, I tapped the gas as that usually solves the problem. Although just as I did that I had a misfire code for the #1 and #2 cylinders. Cleared the code and have not had the misfire code since.
I have already cleaned the IAC, and that has not made a difference. I have new plugs coming next week, although I am doubtful that will be the sole source of the issue. The fuel filter has been replaced since the problem began, and the last thing I have yet to do is an FPR.
Can anyone out there suggest any other possibilities that I need to look at? The only other thing I can think of is swapping coil packs, although by not throwing misfire codes it would be difficult to determine if that is the issue.