Car will start but will not idle unless you apply some pressure to the throttle.

Recently had trans. Rebuilt. When I got it back it overheated and the ignition stopped working. After 400$ in repairs we finally got the ignition workin ( it wound up being a steel rod that actuated something in the column, it slipped out of place) and now you can turn the car on but it will not idle. The shop we took it to said that it was running very rich. My only drawback is that before I had any work done the car ran okay, it always started, always idled, and only had a slight shimmy in the motor somewhere when accelerating through 38-43 MPH. Now I can't even keep the car running. I inspected the engine and everything seems normal but then again I'm no pro. So the current symptoms are: 1st: ignition on ( car running ) stalls 2nd: No illumination in climate control display ( new symptom ) 3rd: The only way the car will idle is at 1000 rpm in park 4th: Car should idle between 650-800 rpm in park *( it dies at this range ) 5th: Stored code in engine is E059 My main concern is why it wont stay at idle. Replace ISC motor less then a year ago as well as Spark Plugs and Wires, Rebuilt transmission 3 months ago. This is a 4.1 Cadillac Engine EFI/TBI