I have a 98 Grand Cherokee 4.0 2WD, it would start and run for about 30 sec then sputter and die, if I kept it accererated manually at about 1200 RPM it would continue to run ok until i allowed it to idle and again it would sputter and die, sometimes continue sputtering after the key was off also.
Sometimes it would start right back up and other times it would crank and crank and eventually start.
I changed the crank sensor and it did the same thing.
Now it will only crank, no fire, I am getting good fuel pressure when I turn the key on and it continues good as i crank.
I am getting no spark at the plug wires and no spark from the coil wire.
I put a volt meter on the 2 wire connector that feeds the coil and when I turn the key on i get a 12 volt spike then it drops to zero, as i crank i get variable readings from about .10 to .23, no where close to even one volt.
Well, I've never had IAC problems (knock on wood) but I've heard that you can hear it work. You could try to listen for it. The IAC has a pair of solenoids that make a noise when working. You'll need a stethoscope to hear it though. You might try unscrewing the 4 bolts that hold it down 1/8" and see if that makes a difference as well. There are quite a few threads on here that talk about diagnosing IAC problems. I would search "Idle Air Controller" on here and see if one of those threads could give you a better understanding of how to diagnose it.