1991 Cadillac Deville defaults to idle

First you need to clean out your throttle plates, use 2 cans of carb cleaner to clean them, there probally black inside, open them way up and ck the 2 tubes down inside the intake throat and see if there plugged also, ( these are EGR tubes) clean them with a coat hanger. After that you need to back probe the TPS with the ISC motor fully retracted and then unplug it( a 4 or 5 wire connector), your looking for a voltage of.5 volts no more no less, loosen the TPS screws a little to adjust it. An idle relearn will need to be preformed after that