Runs rough at idle

What is your question?

Most of the time fires right up, runs smooth for 20 seconds, then would tend to die if I don't nursemaid the throttle. After warming up it tends to run smoother, but gas milage is bad. Mechanic has replaced oxygen sensor 234-4776 and 234-4777 with PO 140 light on. Also has replaced mass air sensor xtp410088 with light po171 on. So far $1000 and still a problem. This last week with cold temps 3 times would not start in garage. Plenty of battery but no attempt to turn over. An hour later it would fire right up. Any thoughts.