Rough Idle/cuts out when put in D or R
 

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?

Is there any chance you put plug wires back on in the wrong order? I did that once and didn't figure it out for two sets of plugs (thinking it was my new spark plugs). Car was hard to start and ran horrible finally bogging down and then wouldn't start anymore. I just had two wires swapped.

I think sptt might be spot on with this one. Make sure you have the wires in the right order.

1988 300e
 

Thanks for the tech help, redid the spark plug wires, idles smoother, I still have a problem when I turn my steering wheel any direction, the idle gets weak and cuts off, same thing happens when put into drive or reverse, but starts up again in park or N.:confused:

The power steering part I don't get. Can you check your voltage regulator in the alternator or have you yet? Something is putting a drain on the system. Not sure how the power steering would cause it to happen unless it is vacuum pressure related somehow.

Thanks sptt
 

You were right sptt, it was the voltage regulator in the alternator, i removed it saw white and smoked areas on lead contacts, it looked very old, i brought it in Texas during my trip across crountry, from the west coast to the east coast, it was rebuilt and about three years old, being that new i never suspected the alternater was poor quality. I replaced the voltage regulator with a used one it cranked and i was able to turn the steering wheel and drive forward, now on to the parts store to one of great quality. In my efford to find the problem i tinkered with everything under the hood and passenger seat, it runs very rough must work on smoothing out the :)idle before i drive on the srteet.:) Thanks sptt, you are the best !!

You are very welcome. I am glad to hear I was able to help. Your next step is to check those air idle hoses on the Idle Control Valve (for vacuum issues that cause idle and rough running engine) and to clean off or replace your O2 sensor which is underneath the passenger footwell side accessed from the inside and underneath.