I removed oil filter stated car split second turn back off to see if oil pressure was there. I did check the levels, just placed new radi on last year .

I drove the car thinking the gauge was broken. the car was at idle for about 5 minutes on zero before I started driving. The lifters started making noise and i pulled off road shut engine down. rechecked oil all ok. The next day I took oil filter off to check pressure, oil gushed split second shut engine off cleaned and placed filter back on. restated to get a 3 on level after about 7 minutes at idle lifters started again but stoped . There is not any knocking but the pressure when foot on gas idle 2000 rpms goes from 3 down to 2 which i think is the right area to 1.5. I let off the gas and turned off car.My oil level ok, water ok,

has anyone heard of this oil pressure problem from a 5mph fender bender ?