1998 Dakota 3.9 4WD Auto (80k miles)
Truck starts and runs perfect when cold. When you try to restart it hot after shutting off, it sometimes has trouble catching the idle after the initial rev up on start.
If I give it throttle and slowly ease off it will catch and run/drive perfectly. Always fires off no problem and responds to throttle, just struggles to catch the idle most of the time.
Sometimes struggles to idle for a second when letting off throttle.

IAC was replaced. AIS command test was good.
Fuel pressure solid 45-50psi at all times, stays above 42psi after shut down for 5 minutes
Vacuum test was good
Manifold Vacuum 19.1-19.4 inHg
Barometric Pressure 29.5 inHg
MAP is 4.5v Key on Engine Off, 1.3v at idle
TPS is .63v no throttle, 3.67v full throttle
CKP & CMP good & verified
IAT good & verified
Coolant Temp Sensor good & verified
Upstream 02 is 0.2v - 1.0v
Downstream 02 is around .45
Purge test was good

When I disconnect/reconnect the battery, usually starts right up hot. Then after idling for maybe 60 seconds, restarting has the idle problem again.
New battery was tried, no change.
Throttle body was cleaned
Had plugs and wires a few months ago
Had CKP replaced in August
Fuel is fresh

Problem started 2-3 weeks ago

This is racking my brain, any help is appreciated.

 

Did you clean the throttle body when you changed the IAC motor?

Also, these trucks don't really play nice with aftermarket parts of that nature.......

 

Cleaned the throttle body, and the IAC was an aftermarket one but passed the AIS command test on scan tool.

 

I put an aftermarket IAC on my truck. (my 96 5.9) It 'worked' sort of..... I had occasional stalling, regardless of temp, and I sometimes had to step on the gas to get it to start. I pulled a mopar IAC off of a spare motor I had layin' around, swapped 'em out, reset the PCM, and all of my problems went away. Will it work for you? Don't know.