Mercedes Benz repair: 1988 Mercedes 190e 2.3 auto. trans., fuel pump relay, oxygen sensor

Question
My car randomly stalls out. Most of the time it happens when I slow down the car, e.g.,  to stop at a red light or make a turn. It has also occassionally stalled out while driving; this happens only when I am driving on local streets - it has never happened on a highway going above 50 mph. A couple of years ago my mechanic replaced the overload relay when I had the same problem and that resolved the problem. He replaced this relay again and it did not prevent the stalls. Right now my mechanic is stumped but he will be doing more tests. Do you have any suggestions? Thank you

Answer
All of these, or a combination is possible.

Air Temp. Sensor
Altitude Sensor
Alternator
Battery
Catalytic Converter
Cold Start Valve
Distributor Cap
Distributor Rotor
E.H.A. Valve
Fuel Pump Relay, Test this with great care = it is a common issue.
Fuel Filter
Fuel Pump
Fuel Injector
Fuel Injector Seal
Ignition Coil
Ignition Wire
Idle Control Valve
Kickdown Switch
Oxygen Sensor
Reference Sensor, a failing unit will fit your symptoms.
Water Temp. Sensor