I have a 04 Tahoe with 245k on the drive train in the past 6 months I've replaced the fuel pump, fuel filter, plugs and wires, knock sensors, intake gaskets, rear main (engine), and oil pan gasket. When I first start the engine the oil pressure is fine but after a few minutes (before it fully warms up) and I stop for a red light or traffic the low oil pressure warning msg appears, the valves start tapping, and the gauge reads zero. I can put it in neutral give it a little gas and the pressure comes back up the low oil pressure warning msg goes out and the valves stop tapping. After a few miles of driving and its fully warmed up I can shut the truck off and on and never have the problem again for the rest of the day. I read that changing the intake gaskets should fix this problem however its still occurring. any suggestions on what to check next?
The oil pressure while driving at highway speeds is approx. 45 to 50 and at idle it 35 to 40.
TIA

 

either the oil pump is bad or the engine is worn out...all the bearings probably have to much clearance.

 

The motor is probably getting to the end of its lifespan and in hind sight being its 20-20 I should have changed the oil pump when I had the oil pan off. She still has gobs of power though so that's a good thing!