The oil pressure surges all the time and sometimes when I come to a stop and sit at a light in gear the oil pressure drops to 0 but the motor makes no excess noise or change it idle. Car runs perfect even when it drops to 0. Can the oil pressure sending unit be faulty? Is there somewhere I can be losing this pressure without there being a change to the behavior of the car? It seems to run fine even at 0. After a while the gauge works again. Any help is appreciated. Also where is the pressure sending unit?

Car is a 1993 Z28 A4.

 

You could have a faulty sending unit, or (less likely) the pickup is fallen part way off or something similar. I would check the pressure sensor first. Shoudl be right up above the oil filter on a 93

-Shannon