Originally Posted by
Injuneer
Do you have your EGR system still in place? There is evidence of fractional degrees of knock retard, and this occurs at the same time the EGR duty cycle goes to 100%. The 100% EGR seems to lag the knock retard by one frame of data. It's almost like you are getting knock retard, and immediately, the PCM opens the EGR to try and cool down the combustion chamber and control it. If EGR led the knock retard, I'd look for a leak in the EGR vacuum system, but that doesn't seem to be the case.