Sometimes during the cleaning process, as sensors are being cleaned up, the ECU or computer that translate all this information, may change fuel to air ratio, or perhaps even idle speed. A drop of 100 to 125 rpms at idle speed would cause a decrease in oil pressure at idle. The fact that it is still producing 40 PSI at 2000 rpm’s or so on the highway would indicate good pressure and circulation. Or sometimes the oil sending unit is receiving and sending new information from cleaning.
