Driver may experience poor acceleration and throttle response on DD engines. Code SPN 2659/FMI 1 EGR Flow Target Error Diagnostic/Low Flow may be logged, but at times no codes may be logged at all.
This may be caused by plugged ports in the EGR Venturi Pipe. This slows down the response of the sensor but sometimes produces no codes because the unit is in Smoke Control, often for several seconds at a time. This will cause no throttle response or poor acceleration.
Clean the two Venturi ports and replace the Delta Pressure sensor.