Rough Idle/cuts out when put in D or R

[jesse j. jeter]

I have a 1988 Benz 300e, I decided to replace the cap and rotor for maintenance, car was running find. But after i replaced the cap and rotor it would not crank, i heard belching and it smoked, its been down four months now. I purchased another rotor and cap, fuel filter, air cleaner new wires,plugs,new throttle cable, checked every vacuum hose i could find, tried a another used coil, used EZL,replaced the crank sensor,coolant temp switch, switched out fuel pump relay, OVP replaced, new o2 sensor, finally i replaced the cold start valve it cranked, but ran so rough i thought i would break my motor mounts, i brought a used Bosh fuel distributor unit with everything attached black box and throttle body, still cranks but runs rough, cuts out if i try to shift into D or R.It does smooth out somewhat if i push down on the gas peddle. Also there was a strong boiled egg smell during cranking attempts. I maintained it for 6 years, replaced cap and rotor before even belt, no problems, has anyone any idea as to what is going on?