My W124 230TE has the same motor and the same problem.
I assume the oil is a bit of blowby.
The hose on my engine appears to have shrunk a bit as it doesn't quite reach all 3 attachment points.
I doubt it would effect idle quality.

How rough is your idle ?


Doug MCcUTCHAN
1987 w124 230te
1983 w126 280se