I am having exactly the same simptoms like you have described on my s420 1998. On top of that the engine is not very smooth at idle.
Same simptoms with the cilinder bank and my mechanic told me that the left side chain is stretched.
I still have the check engine on.Problem unsolved yet.

__________________
New Addition to the family
2013 Passat TDI 5Miles
2004 E500 4MATIC Wagon 95k
1996 E300 Diesel 173k Sold
1993 300E 2.8 230k Sold
1994 E320 White Wagon 373K Sold
Still dreaming about ....500E


Radu Negru