95 Firebird: oil pressure drop

Hi guys
I got Oil pressure issue with my 95 firebird. The oil pressure is fine initially when I start the car but when I drive it for a while and come to a stop sign the pointer on the gauge drops all the way to zero and the "check gauges" sign turns on. But if I drive the car for little bit, the pointer goes up a bit and drops to zero again if the car comes to a stop or is driven at lower speeds.
The engine does not make any weired noise and I did not see any drop in horese power.

I rescently put a motor in my car and the oil pressure sending unit(OPSU) broke while installing it . So the mechanic put the OPSU from the old motor.

The mechanic says that the oil pressure drop is due to the oil seeping through the bearings or something and eventually its gonna damage the cams and other moving parts due to insufficient lubrication.

Some other guy told me that the problem my have occured due to messed up OPSU.

My question :
1. Has any one witnessed such drop in oil pressure problem?
2. And if they did how did they resolve the issue?

thanks.

Could be alot of things. If you can try a mechanical pressure gage and see if the pressure really is dropping that low. You say you put a motor in it, another possiblity is the oil pickup may have come loose in the oil pan.

Axaa, mine does the same thing! After you let your car sit for a few hours it starts all over again? I'm not getting any noises from my engine at low pressure either, and when I gun it, it goes back up a good bit until I let off the accelerater. I was considering changing the sending unit, if you figure it out, lemme know!