Fixing the Idle Air Control (IAC) Motor
We all know each of these cars has is own quirks, but, the following may be of some help (if you have access to SCT) to get around problems with the IAC stepper motor. The issues can be erratic idle and/or stalling when de-accelerating. The IAC motor is basically what sets the idle thru the PCM. The PCM will also vary the timing to help with idle control.
I have never had a problem with the IAC, but, ever since installing the 1.7 rockers the idle has been way too lumpy for 672 rpms, that was the factory idle setting on my 97. When I obtained the SCT Pro Racer package the first thing I did was increase the idle to 750. That worked quite well, but, I made a mistake by not paying attention to the IAC control settings, they should have been changed at the same time as the change to the base idle.
I put in a cam late last year and never had time to fine tune the car, but, right after I installed the cam I started having a stall issue when de-accelerating and coming to a stop. I thought it was either due to the IAC motor going bad or the fact that I lost some idle vacuum with the new cam or a combination of both. I ordered a new IAC motor, but, before installing the stepper motor I reviewed the settings for the IAC system within SCT. There are approx 6 control statements for the IAC within SCT. In affect, you can do a lot to tailor the way the stepper motor reacts to various engine inputs. The main mistake I made was not setting the de-acceleration rpm when coming off of cruise. The oem de-acceleration rpm (700) was actually lower than my new SCT custom idle rpm of 750. It was this push/pull that caused my stalling. After setting all the IAC parameters the car runs fine, perhaps better than ever before.
In summary, if you have access to the SCT software you can probably fix many of the issues associated with the IAC.