Q: Jeep stalls while parked at idle and when going down the road when the throttle is closed.

My 1983 jeep has a 4.0 inline six from a newer Jeep product. It had always run well except that you had to give it a little bit of pedal to get it to start on cold winter mornings. This Jeep is a daily driver and is parked outside. I wanted to be able to start it up without having to give it gas. A neighbor of mine who claims to be an expert, suggested that I cleaned the throttle body and Idle air control valve. After cleaning the throttle body and IAC, the Jeep starts up great without having to push the accelerator pedal. The problem is now the engine will stall after 2-5 minutes of idling, it usually will start back up easily but sometimes it will not restart without holding the accelerator pedal to the floor. The Jeep also will stall when coming to a stop while driving, but not every time. I verified that there are no vacuum leaks and have installed to new aftermarket IAC motor and a new throttle position sensor. No change after installing the new parts.

My car has 75000 miles.
My car has a manual transmission.