Cadillac Repair: 1991 Deville idle, throttle plate, chemical spray

Question
My 1991 Deville will not idle when car is in park or nuetral and won't stay running unless I keep a foot on the throttle.  Even when in gear and moving if I let up on the throttle it will lose power and die.  At 50-55 it seems to run just fine but any stop and go driving is impossible because it will stall.  What is the problem?

Answer
Take off the hoses you you can physically see the throttle plate.

2. Use a chemical spray type cleaner such as carb cleaner to remove all the black residue from both sides of the throttle plate as well as the rest of the throttle bore. Also just below the throtle plate when you open up thr throttle plate all the way you will see a small hole in the side of the throttle bore. Spray some cleaner in there as well and see if this resolves your problem.