1991 Chrysler New Yorker- Where is the idle adjustment screw.. or is there one?

Controlled by computer as mentioned by others. If you are having idle troubles then you either have engine trouble, or simply an idle speed motor that is bad. These are easy to change and might be simply gummed up. Take it off and spray it with cleaner and the port where it goes as well. Other than that do an engine and computer check. These idle very well if nothing is wrong with them so should not be running rough idle. There technically is a throttle stop adjustment screw, but that is NOT the idle adjustment. As other's have mentioned it is all done by computer. unless major engine work has just been performed no reason to have to adjust it.