I had a bad coil on my 94 e320. I had tried to check it with an ohmmeter but somehow fooled myself--the internal connection was erratic. Independent tech found it--cost me 3 hours labor!
94 E320 Wagon, 170k, totalled in 2006
2002 BMW 525i Wagon, 75k
1991 BMW 318is (two of 'em)