Sorry to read that you are still having problems with the idle in your 420 SEL...Rough idle is not normal for these engines, at least not that I know of. Since Norman fixed the sticky exhaust valve problem in my 1991 420 SEL it runs just fine. If you tell him that your car is still not running as expected he'll keep looking for the problem, till he gets it fixed...
P.S. Maybe we can meet some day at Norman's and run our engines side by side. Then you could tell whether the situation that you describe is normal to all 420's.
P.S.S. What brand of gas do you use? I find that my car runs "happiest" when imbibing Chevron Supreme. It does OK with Union 76, but it doesn't like any other brands. One time I stopped at a "El Cheapo Discount Gas" and put in about a 1/4 of a tank. My car was definitely not happy with the cheaper gas and it let me know about it. After running a full tank of the usual Chevron Supreme, the car went back to its usual self.
[Edited by BENZ-LGB on 06-10-2001 at 10:10 AM]
1989 300TE "Alice"
1990 300CE "Sam Spade"
1991 300CE "Beowulf" RIP (06.1991 - 10.10.2007)
1998 E320 "Orson"
2002 C320 Wagon "Molly Fox"
Res non semper sunt quae esse videntur
Not in this weather!