Is the new IAC aftermarket or a Mopar replacement part? There have been issues with aftermarket IACs not functioning properly out of the box.

Also, have you scanned the PCM with a OBD2 scanner? Any stored or pending codes present?

 

Mopar, new. Functioning properly. The only code I have is a P0441 which I’ve tried to locate, but haven’t been successful. The lines are intact, the solenoid, and canisters are new. I’ve replaced them twice.

 

The lines dry out and crack, and it isn't obvious...... Gotta do a pretty close inspection, or a smoke test to verify the lines are good.

 

I did. Trust me when I say I’ve ran every test available. Right now I’m going to replace the crankshaft position sensor with a mopar branded one. The last one was a “Holstein” aftermarket sensor.

 

Named after a Cow?????? Oh, yeah, that's confidence inspiring.

 

P0441 Evap Purge Flow Monitor
Have you cleared the code? If so does it come back? You may want to go into more detail of what the "Vibration/shudder" is. My thoughts are if it acts like it's not running on all 8 cylinders it's most likely an ignition related problem. A vac leak will cause the engine to raise the rpm(not considered a " Vibration/shudder". Did you happen to check the vac hose coming off the throttle body that supplies vac for the evap system?

 

I’ve cleared that code like 10x and it returns. However, I think I solved the issue. The new valves were defective. I installed a mopar one, and it hasn’t came back. The thing is, the RPM’s do not bounce at all, and it’s mainly in the front end. I personally believe it’s a mechanical issue such as a fan blade out of balance or something.

 

You can take the belt off and see if it's still there. Also look at the balancer, The outer ring tends to move when the rubber deteriorates. But i don't think that would cause the issue you are explaining.