Does anyone know what the INPA engine roughness test actually measures?
My results are as follows, but not sure how to interpret. I swapped coils around (from off zero cylinders to others), but limited change...
Results: Car is E39 528is (M52 Single Vanos. NOT Nikasil Block)
engine rougness when at 90.5oC.jpg
Thank you anyone in the 'know' !