Another Idle problem

[twocontours]

95 contour duratec, 86k miles

Car developed an intermittent idle problem. At random times it drops from a steady idle to just about stalling then recovers. No audible vacuum leaks, tried spraying carb cleaner but can't find a location that causes the problem to go away with any consistency (it's intermittent so when it goes away it may or may not be the carb cleaner). Idle drops to zero (engine shuts off) if I remove the IAC connector. No codes. EGR valve operates normal when I pull a vacuum on it. Vacuum gauge reads normal but vacumm drops as car stalls but I don't know if its cause or effect of stalling. I'm out of ideas and ready to replace IAC on a hunch but my hunches are usually wrong and expensive.

Help

 

[Tony2005]

How old is the IAC valve? If it is more than 10 years, it is time for replacement anyway. Don't forget to get a new gasket too.

Idle issues are almost always due to vacuum leaks. Have you tried cleaning the MAF sensor?
http://www.contour.org/ceg-vb/showthread.php?t=563

 

[twocontours]

Cleaned the MAF about 3 months ago. Doesn't seem like dirty MAF since it either idles fine or is stalling, no middle ground.

 

[Tony2005]

... tried spraying carb cleaner but can't find a location that causes the problem to go away with any consistency (it's intermittent so when it goes away it may or may not be the carb cleaner). ...

I just reread your OP. The carb cleaner will make the engine idle faster or slower for a few seconds and then return to its "crappy" idle. It won't "cause the problem to go away with any consistency". Yes, you have to listen carefully to detect a change in the engine RPM with spraying. I suggest you check the Intake Air Temperature - IAT sensor too.
http://www.contour.org/ceg-vb/showthread.php?t=4170

 

[twocontours]

It's really hard to tell if there is any change with the carb cleaner, the rough idle is intermittent, more like a stumble for 5 to 10 seconds then it recovers. I can't tell if the carb cleaner is having an impact or if the stumble is just going away on its own. I hate intermittent problems, especially on a car with a wiring harness made from talcum powder.