When using the '7427 how do you get the IAC to zero out? I've followed the procedure you can find a 100 places online: jumper A&B on the ALDL, turn the key on, and then go unplug the IAC which should lock it in with the pintle completely closed. but I don't think that's happening. SES light is blinking fast, so I think it is in diagnostic mode, but no sound is coming from the IAC and I don't think it's closing.

This method always worked on my 7060 PCM, but I've found threads on here and elsewhere that make it sound like GM changed the diagnostic procedure when the 7427 came out. But those threads did not give me info about what that diagnostic process is. I'm probably missing something obvious.

I did find a recent thread with the 20 lbs paper trick (Dave W). Cut a 1/2" wide strip of 20 lbs normal paper. Set the throttle stop screw so the paper drags when pulling it out from between the throttle blade and the bore. I did that and drove it and it seems to be idling pretty good, but I didn't have the computer out there to log IAC counts. Will do that tomorrow. Maybe they will be low enough that I don't need to further mess with base idle.....