How do you repair a cold start rough idle for the first several minutes on a 1986 Buick Riviera?

I had to try one additional part. I thought the pressure regulator resolved my problem. With an outside temperature at 45 degrees the car started up great. An outside temperature at 65 degrees caused the car to stall after the initial start-up. The intake air temperature sensor ($16.00) was replaced and this solved my problem.