starting problem

[dtrain]

In regards to my '89 420 SEL, I have had recent problems when attempting to start. The engine will turn over but will require an extended turn of the key. Once the car starts, it will idle roughly and shake for aproximately 20-30 seconds. Applying the gas lightly once the car starts seems to help the problem but is not a cure.
I have replaced the following parts in an attempt to correct the problem: spark plugs, wire set, distributor cap and rotor, fuel filter, O2 sensor, and air filters.
I have searched the archives and found numerous threads with this topic but I haven't found one that seemed to address this problem.

dtrain

[algae1]

I am fightin the same problem on my 560SEL and i have not found the problem yet. Some things to look at further that come to mind-
1)check the coolant sensor and the resistance values
2)check the EHA valve wiring and resistance (it should be about 19 ohms).
3)check the idle control valve wiring and resistance (should be about 5 ohms).
4)Check the OVP relay and fuse.
5)U should also check for fuel pressure leak down.

Good luck and hope u find it.keep us posted.

With mine the idle is very rough until the system goes into Lambda and then it smooths out and speeds up. If i restart immediately it starts right up. If i let the car sit for 45 mintues is starts hard again. Scratchin my head still.

[Cap'n Carageous]

Same thing with my 300E. I don't think i'm getting power to the cold start injector.