Idle issues on a 3.0

[SoCalJack]

I have idle issues again. I have a 1975 with a 1983 transplant engine (3.0 Liter engine). I drive the car once a week and the following pattern happens. When I start the car in the morning it usually takes 2-3 try's before starting. Usually on the third crank it will catch and I give it a little tap on the gas peddle and it will start. At this point the car idles high at a steady 1600-1800 rpm. I let the car warm up for about 10 minutes and then I drive another 15 minutes to get some coffee. At this time the idle stays at the 1600-1800 rpm. I stop the car and get my morning coffee and read the paper approximately 15 minutes. When I'm done I get back into the car and it starts right up however, the idle is very low to the point where if I don't keep my foot on the gas peddle it will die out. I manage to get the car on the freeway for a another 15 minute drive in to work. When I get off the freeway and on the streets the idle is near perfect at around a steady 900-1000 rpm. When I go home after work this pattern repeats except the starting rpm levels seem to be a bit lower 1400-1500 rpm. One more piece of information not sure if its connected and that is the O2 sensor is not connected. What does this sound like to all you experts. Other than the idle issues the car seems to running great pulls strong and no smoke. Thanks