Lawsonmh15 Posted September 17, 2005 Share Posted September 17, 2005 I have been experiencing a dip in mileage and have taken care of Plugs, wires, etc... Heard that the ONLY O2 sensor that affects your mileage and performance is the Pre-cat (3-wire). However, a parts person at a Sub. dealership said that both are of equal importance. However, I can unplug the post-cat and no CEL is thrown??? Basically, I need the straight poop on O2 sensors. FACT not OPINION please. It seems strange that the post cat (4-wire) would cost 2-3 times more, but not have any affect on performance. TIA. Also, could a universal 3 wire be adapted to the 4 wire? I know you'd lose a lead (Most likely the ground) but don't know if that would cause problems, or if the loss of the negative rail is inconsequential as this is DC not AC power. Link to comment Share on other sites More sharing options...
86subaru Posted September 17, 2005 Share Posted September 17, 2005 same here replaced 02 with after market , the oem in there looked bad but no codes , mpg went down 1-2 mpg , so i think i am going to put old oem back in Link to comment Share on other sites More sharing options...
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