1991 300E Hard Start and dies

After it warmed up, this car would die at stops; and then be hard to start. The shop cleaned the Idle Speed Control Valve and said that if it was this part, it would readjust itself. I only worked for a couple of weeks. so, I bought a used one (online as a new one costs $300-400) and installed it this morning. It was very hard to start, and when it did, it died when I pushed the excelerator; and would not start again until I tried later in the day. The same thing happened...hard to start and died.

One of the writers, at this site, had a similar problem. He replaced the Fuel Pump and Filter, to no avail. The shop said it was a Crankshaft Position Sensor - but he has not yet updated to whether that worked out or not. Do any of you have any insight? Could it be the Fuel Pump, Fuel Relay, Fuel Accumulator, or even the Cold Start Valve - as it was not warmed up this morning after I replaced the Idle control valve)??