I've made that mistake several times on my W124...and it would take over a week for stuff to sort itself out!

Primary breach would be water penetrating the ignition cover. Water probably "pools" around the coils and spark plug wells...the misfiring is dramatic!!

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car