It doesnt sound like oils is low, but hard to tell wth the chimes. It rus well for a while and then drops.
Welcome to Just Answer.com. I'm here to help you and your 100% satisfaction is my goal. Please Accept if you are satisfied.
There would need to be some testing done here as there are many things that can cause low oil pressure. One of the more likely in this case would be a restriction of the valve lifter oil manifold (VLOM) filter. The proper procedure would be to install a special tool where the oil filter is and read the pressure there. What we are are looking for is if proper pressure is available at the lower end but only the sensor or VLOM is not receiving it. Has the vehicle been serviced regularly and there is no sludge build up in the system? There can be bearing clearance issues caused by wear, oil pressure valve sticking issues, or issues in the VLOM. You didn't mention any knocking or ticking noises. Are there any?
Thanks. Additional info will help lead to the correct answer.