So,

I have been encountering some odd idle behavior as of late and I am hoping for some help. My weird cold start high RPM (2000 RPM for 3-5 seconds) continues, but I don't think its related but I mention this nonetheless as a reference. After I have been driving in the morning for two minutes or something I have a wandering or surging or hunting idle at stoplights. It feels like its oscillating between getting fuel and not on and off at half second (or thereabouts) intervals. on the high end it will be something like 730ish RPM, I really cant tell what it is when its too low. You might also compare it to an invisible hand tapping the throttle cable, but the gas analogy feels more true. Once the truck is warmed up it doesn't seem to do this at all.

Recent replacments were:
MAF (new secondhand one)
Plugs + wires
O2 sensors (all)
IAC valve/motor

I reset the ECM adaptations with my hawkeye to see if there was something to that, but it didn't seem to help very much.

any ideas?

 

Do you have SAI?

 

Yes I do,

Sorry, I neglected to mention, its an 03 4.6 w/SAI.
It should be noted that this happens after the hair dryer turns off.

 

Does the internal part in your IAC motor spin freely? If it sticks it could cause a crazy idle. Any codes popping up? I had one D2 that would almost completely die or sputter and I had no fault codes. It finally finally set a fault and it was for the darn purge control valve! Slapped in a Hyundai unit and it idled fantastic after that and never tried to die again.

 

The IAC "spins" or moves back and forth freely, If i wiggle the whole thing in my hand it goes clicky clicky as it goes to both ends of its travel, it looks clean in inside also (i cleaned it)

the codes I get are:
P0171
P0174

 

With those faults I'd look for a vacuum leak, SAI line leak/stuck valve, or an exhaust leak.