IAC dead?

91/4.0/AW4 223k

Recently my XJ has begun stalling out on me right after reaches operating temp. It won't then start again for a minute or two even if I try to crank it over.

I've replaced the CPS already, however I also notice a hissing noise coming from under the hood every so often.

Sometimes my idle is raised to 1000 rpm as well.

Finally, I've tried unplugging the IAC to see if it would make a difference (aka make it run rougher). I'm not sure if it should or not, but it makes no change.

Any help on this one?

check the small vac hose coming out of the intake that hose came undone and case me idle and stalling problems.

Which small vac hose? The problem seems to be getting worse.

My real question is should my idle fluctuate if I unplug the IAC?

Should I try unplugging the O2 sensor and see if it dies out?

No it will not cause a change if you disco it while running because the plunger is already "set"

My 89 has had the iac disconnected for the better part of two years.....runs well without it and my rpm's don't shoot up to 2800rpm after startup anymore.

I disconnected it with the jeep idleing so that the plunger was set for idle.if you disco it while the jeep is off your rpm will not be right because the plunger automatically gets reset via the latch circuit when you shut it down....so this may be a way to verify if indeed it is working.Unplug it with the jeep off and then start it up and note wether or not your rpms changed...