WARNING: This page is about a different car, the 2008 Mazda RX-8, 2007 Mazda RX-8, 2006 Mazda RX-8, 2005 Mazda RX-8, and 2004 Mazda RX-8. However, it is still accessible from the selected car via links, so may be relevant.
Measure the clearance between the inner rotor and the oil pump cover.
If the clearance is not within the specification, replace the inner rotor.
Specification
0.02-0.04 mm {0.0008-0.0015 in}
Fig 1: Measuring Clearance Between Inner Rotor And Oil Pump Cover