O2 sensor problems?

[Jedi276]

The problem I am having is with a 2001 mustang GT. For the past few months occasionally my car would for some reason refuse to idle, but after driving it for a little bit the problem would clear and the car would act fine. On Monday I had the problem again, but the problem wouldn't clear, so I took it to a Jiffy Lube to have them run the codes for my SES light (it is always in due to not having catalytic converters). The codes he pulled were:
-P1130: Lack of Upstream Heated Oxygen Sensor Switch - Adaptive Fuel Limit - Bank No. 1.
-P1131: Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1.
-P0171: System Too Lean - Bank No. 1.
-P1507: Idle Air Control Under Speed Error
On Tuesday I looked at the O2 sensor on the passenger side of the car and the wiring was terrible (exposed wires, insulation burned off by long tube headers). I pulled the O2 sensor and just replaced the wiring, then started up the car again, at which point it would idle, barely, and at 400-500 RPM. After a day of driving on it the SES light came in again so I just had the codes pulled once again and they are:
-P1507: Idle Air Control Under Speed Error
-P0420: Catalyst System Efficiency below Limit - Bank No 1
Today I tried to just disconnect the battery for a while and let the computer reset and then start it up, but it is having the same problem (incredibly low idle). Any ideas on what I need to do to get the car running normal again? My wife thinks she sees plenty of white smoke coming out the back, but I think that it is mostly when it is just running cold (not to mention in DC it is like 30 degrees out). Any help you guys can provide would be great! If not I will probably have to bite the bullet and take it to a dealer for diagnosis. Thanks for the help.

[Blue)(Fusion]

Check the IAC valve on the back of the intake plenum. These are known to get dirty and stick or fail to open/close as commanded.

[Jedi276]

Once I remove the IAC, is there an easy way of checking to make sure everything is ok with it?

[Blue)(Fusion]

Except applying the proper voltage/duty cycle, no not really. I just spray it down real good with some carb cleaner and re-install. Some say that while the engine is running, tapping it with a hammer can unstick it in some cases.

[Jedi276]

She is purring like a kitten again, thanks for the help.

[Blue)(Fusion]

The IAC valve was the culprit? Good to hear it's back to normal!