This is on a 2003 Ecotec. Every mod I did to my car made it run richer. I fried 2 catalytic converters in 4 years. At one point I even installed a SAFC-2 to try to tune down the fuel and that didn't work. Recently I removed the cat and put in a resonator but kept the stock second O2 sensor. Monday I removed the second O2 sensor and put in a wideband. Wednesday I get my friend to use HP tuners on it. He did some basic stuff, turn off the codes for the second 02 sensor, and did a little tuning with the upper level rpm/map table.

Mind you, he didn't touch anything under 4000 rpms on the table. Since wednesday I've put on over 100 miles and the car is running great. In fact, it's finally running a tad on the lean side. Before the tune, it was definitely running richer when looking at the wideband.

Here is what tis boils down to: Is it possible that over the past four years, I've had a bad O2 sensor? Is there a way to see? Maybe this is speculation, but I'm just curious what you guys think.



http://www.cardomain.com/ride/676422/1

There's really no way to tell unless you still have the old O2 sensor. It's normal for the ECU with a stock tune to enrich the mixture a little when you start bolting on High flow exaust and intake parts. Having a bad second O2 sensor really shouldnt effect much, it uses the one in the manifold to read the exaust mixture, the second one is mainly there to see if the cat is working.

J-s run rich from the factory anyway. so that probaly affected your MPG.
then what some people do when adding intake, exhaust, whatever, they reset the computer but then they floor the gas pedal everytime they can. the computer then learns to dump extra feul when its not needed.



Im a Xbox 360 fanboy...and damn proud of it!!