Many mechanical devices on these engines throw a diagnostic code, the IAC is one of them.I just replaced one on my 4.0 engine, it was stuck and did not operate smoothly! It's a stepper motor running a lead screw to adjust mixture, I had the same symptoms you are having now!
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The Mapp and air temp sensor do not throw codes either. Iac doesn't throw code. Straight from 1994 factory service manual! You can monitor with good diagnostic scanners!
Many mechanical devices on these engines throw a diagnostic code, the IAC is one of them.I just replaced one on my 4.0 engine, it was stuck and did not operate smoothly! It's a stepper motor running a lead screw to adjust mixture, I had the same symptoms you are having now!