I tried to unhook the wires ISC and turn the lights on when the engine is not fully warmed up. Indeed, she felt a drop RPM to about 400-500rpm and the engine is "troubling." Apparently, not well calculated transmission crankshaft pulley and alternator pulley. Loads on the crankshaft of the alternator is still too high when the engine is cold. But it was 1989 years 
On newer engines that have been resolved in a different way. They realized that it is better to use the classic stepper motor which can be accurately leveled airflow compared to previous solutions with solenoid it works quite imprecise.
Interestingly, the ECM does not attempt to correct RPM-based information about drop RPM, but it works on the basis of information included heavy consumers (light, fan, heater, etc.), or very low temperatures. In the case of low-temperature "role" will take over and termic "IAC".
I think there is a mistake made in the project. So, if the engine is very cold, the IAC opens part of the air. Also it works and ISC parallel together.
If the engine has warmed up, the ISC will be activated for a short time and it will be shut down until they include some of the consumers of electricity. (Information sent with diodes patch terminal, according to ECM)
This is where "holes". If the engine is only partially heated, it still lacks the necessary power to the alternator idlle turned effortlessly. In this case, the ECM does not attempt to correct RPM at this point based on the information obtained from the ignition coil. ECM is "expected" to IAC solenoid starts only if included large load current.
A little thinking ..... I hope you understand, since I use google translate
Reading the service manual, you can reach many conclusions ... ISC always working on constantly PWM (Pulse Wide Modulation) at 20Hz. (Yes, 20Hz) So he has two states: Or is ruled out and can not work, or working on constant 20Hz.
Interestingly, regardless of the load, the ECM will not change the frequency of operation of the ISC. A little strange. : (
The information that the ECM receives from the ignition coil, used only to accurately timed fuel injection, but not for it to compensate for the RPM affecting the pulse width according to the ISC. I do not understand why he made ??this omission.
On newer engines that have been resolved in a different way. They realized that it is better to use the classic stepper motor which can be accurately leveled airflow compared to previous solutions with solenoid it works quite imprecise.
Interestingly, the ECM does not attempt to correct RPM-based information about drop RPM, but it works on the basis of information included heavy consumers (light, fan, heater, etc.), or very low temperatures. In the case of low-temperature "role" will take over and termic "IAC".
I think there is a mistake made in the project. So, if the engine is very cold, the IAC opens part of the air. Also it works and ISC parallel together.
If the engine has warmed up, the ISC will be activated for a short time and it will be shut down until they include some of the consumers of electricity. (Information sent with diodes patch terminal, according to ECM)
This is where "holes". If the engine is only partially heated, it still lacks the necessary power to the alternator idlle turned effortlessly. In this case, the ECM does not attempt to correct RPM at this point based on the information obtained from the ignition coil. ECM is "expected" to IAC solenoid starts only if included large load current.
A little thinking .....
I hope you understand, since I use google translate Reading the service manual, you can reach many conclusions ... ISC always working on constantly PWM (Pulse Wide Modulation) at 20Hz. (Yes, 20Hz) So he has two states: Or is ruled out and can not work, or working on constant 20Hz.
Interestingly, regardless of the load, the ECM will not change the frequency of operation of the ISC. A little strange. : (
The information that the ECM receives from the ignition coil, used only to accurately timed fuel injection, but not for it to compensate for the RPM affecting the pulse width according to the ISC. I do not understand why he made ??this omission.