2002 Mercury Sable won't idle

My car stalled and would start, but it won't idle. The repair shop replaced the starter, and the fuel valve, I think, and when that didn't work, they spent (they said) about 16 or 17 man hours (which they mostly did for free), and finally came to the conclusion that the computer needed replacing, which could only be done by the dealer because apparently they won't let anyone else have the code to program the new computer, so, seeing thousands of dollars flying out the window, I just bought another car, but, I would like to get this one running so I can dispose of it, I hope you can help. Thank you Don