When I start up my car in the morning, the oil pressure drops to 0 after 2 mins of warm up. I continue to warm up the suv for 5-7 mins more, but I have to keep applying air to the accellerater pedal. Then I pull onto the street. For about 10 mins longer the pressure drops to 0. After that my suburban works fine for the rest of the day. What can I do to fix that problem.