Do you have individual coils for each spark plug? It sounds like you may have a bad one or bad connection causing lower than normal voltage and the knock sensor issue could be related to this EST problem.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7