I read a lot of postings....but I was ready to send an update! While the problem disappeared after disconnecting the EHA valve, it may have been a coincidence. My mechanic thinks it is bad gas (obtained from Kroger in Atlanta). I am bringing the car to my mechanic (Autobenz in Marietta) and have is diagnosed. I was told the EHA rarely fails.....usually leaks (mine shows no sign of leakage). I will report back.

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All the best,

J. P. Mose
1968 250SL
1970 280SE 3.5 Cabrio
1987 560SL
1990 560SEL