Home › Forums › Stay Dirty Lounge › Service and Repair Questions Answered Here › Ash / Crust on only one Spark Plug Bank › Reply To: Ash / Crust on only one Spark Plug Bank February 27, 2021 at 9:42 am #989115 N CParticipant Thanks, Richard. I had thought about both of those tests. What about an intake manifold gasket issue?