Fluctuating idle symptoms

[Burban1990]

Recently replaced the coolant temperature sensor that fixed the high idle I was experiencing. Truck's been running great now that the idol is where it should be but I noticed in the last day or so the idol is surging. Not all the time though and only notice at idle speed in park or stopped at a light. I was thinking it could be idle air control valve or a vacuum leak but I just went through all my hoses and they're all fine. No check engine light and it doesn't do it all the time. And when I park it today it was actually almost pulsating up down up down up down. I have to admit this one's new to me haven't had a vehicle act like this before.

 

[Vbb199]

IAC is too far out of range with initial idle setting maybe?

 

[Burban1990]

I just did a reset on the idle for the IAC and it continued to fluctuate. So then I decided to start it up and keep the RPMs up until it got warm then ran and unplugged the IAC and an idle just fine as soon as I plugged the IAC back in it started to fluctuate almost to the point to where it died. At this point I'm pretty confident the IC is bad along with the fact that it doesn't look like an AC Delco part which I tend to use.