Maybe a weak spark is the culprit? I'm only guessing, but I do know that M119s are tough on their distributor caps. Perhaps by ensuring their serviceability you can at least eliminate one potential problem? Good luck!

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"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo