Idle isn't raising with A/C on

[s1ngletracker]

So I'm slightly annoyed by this... Recently got my A/C system back up to snuff (good working compressor, all new O-rings, new condensor) and the A/C works great, but with my idle adjusted properly (per factory service manual procedure) when I turned on the A/C the car would just die.

I had to jack around with my BISS screw until it would stay running, but with A/C on it only idles at 600 rpm, and with it off the idle wants to jump up to 1100 RPM.

What I've tested/checked/replaced:

New ISC motor, all coils test good
closed throttle switch tests good
TPS is 10.1% closed, 99.6% with the pedal to the floor (per MMCD)
running voltage is 13.6V or so
Tested for boost leaks, I only have 1 small one at the throttle shaft seal.

on the logger the ISC reading is 0 when the A/C is off, and appears to be maxed at 47 or so when the A/C is on. It seems as though the ISC motor isn't really doing anything though, that signal doesn't seem to be getting to the ISC.

I'm completely stumped as to what is going on. The car also has some other weird idle issues. I know it is supposed to 'catch' the idle when you take it out of gear while moving and let the RPMs drop. It doesn't appear to do that with the A/C on OR off, the RPM just drops down to idle, I seem to remember it used to catch at around 1000-1200 RPM or so, until you come to a complete stop then it would drop to normal idle level.

At this point pretty much the only thing left in my mind is the ECU being suspect, perhaps running with a bad ISC previously caused damage to the idle driver on the ECU. My next goal is to find a known good ECU to test swap out to test with. Any other suggestions, or am I on track?

I know that most people who still have 1gs probably aren't as anal as I am about everything working properly and just happy to have the car off jackstands, and likely don't have A/C at all. But hopefully someone can help out here. Thanks for any advice.

[s1ngletracker]

So I just had an email conversation with Steve Piette (who USED to repair ECUs - unfortunately just stopped, bummer; DSM guru since the original Talon Digest) and he says that a huge number of the ECUs he repaired would have bad idle drivers, whether the owner knew it or not. Sounding like that is my issue here.

[twack]

Originally Posted by s1ngletracker

a huge number of the ECUs he repaired would have bad idle drivers, whether the owner knew it or not.

good thing ive had my ecu rebuilt by steve, sad to hear he dosnt do it any more

[asshanson]

If you run a bad ISC for awhile it burns out the drivers on the ECU and then a new ISC won't do anything for you. Sounds exactly like what happened to your ECU.