1986 300E spark issue causing stalling when hot

[mdg404]

My son just bought his first car a 1986 300E on Ebay. We picked the car up and 15 minutes later the car stalled out and would not restart. The owner did not reveal this issue. What we know is that the stalling issue is due to loss of spark when the hot. the following parts have been replaced REPLACED INNER/OUTER TIE RODS ON BOTH SIDES. NEW PLUGS, OIL CHANGE, FRONT FLEX DISK ( LIKE UJOINTS FOR DRIVE SHAFT ). THERMOSTAT, RADIATOR HOSES, COOLANT FLUSH, DRAIN & REPLACE POWER STEERING FLUIDS,(2) NEW TIRES, TEMPERATURE SENSOR SWITCH, FUEL INJECTOR SWITCH AND FAN CLUTCH, Fuel pump and filter. It is at a mechanic that specializes in Mercedes and he has determined it is a spark issue and that it is not coil, distributor, rotor, ignition module. Can someone help us out it is my son's first car and he has used up most of his money.

thanks