I have 2002 Hyundai Santa Fe GLS 2.7 AWD, 143,000 mi, with PO420 cat conv efficeincy (bank 1) CEL. It has no noticeable loss of power(has always seemed a littlle under powered) but has a significant decline in gas mileage (down to about 12.5 city). Could a bad cat cause the mileage change without causing a power loss? Would primary O2 sensors have a separate OBD II code, or could they cause the PO420. The sensors were tested ok but I can't understand the poor mileage. If a new cat won't help mileage, where should I look. Only 35,000 miles since tune-up. Thanks.
have the same problem?
Wednesday, May 4th, 2011 AT 2:31 AM