2000 MPV LX engine light is on now 3 days later. what cause Rpm's 2 not drop

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when driving sometimes the rpm's climb to 5,000 rpm without returning to normal range. If I pull over and let idle for a second in park and then proceed on, the RPM return to normal ranges. Engine light went on had Auto zone check the codes. there were three that came up. Bank 1, Bank 2 and I can't remember the third the dealer kept the print outs I had gotten. They tried to say there was armor all on the sensor so they cleaned it off and reset. but less then a mile down the road the engine light came back on and shortly after I was doing about 50 mph and the RPMS just kept climbing. normal they drop back to about 2,400 rpm at that speed. the dealer keeps all the cars on almost empty gas wise until they are purchased. this has happened twice in the 3 days I have had the car, otherwise it runs perfect