Spoolem

I have an 03 WRX w/stage 2 mods. I just recently replaced my spark plugs with copper plugs. I noticed shortly after that my AFR gauge was reading extremely lean at around half throttle (16.8) but a second later rich up to about 15.2 from half to WOT.

I decided to first go buy different plugs (NGK Iridium), check the gaps and put those in considering that's what I previously had in the car. After installing those I went out for another drive and my car continued to do the same thing at around half throttle.

I'm starting to think that it has nothing to do with the plugs or even ignition but rather the fuel system or something wrong with the tune or ECU. I think it's just a coincidence that this leaning out problem started right after I replaced the plugs.

Any thoughts, questions or ideas as to what the problem may be would be great!?

***BTW... My check engine light has yet to come on and while driving the car under half throttle, it runs perfectly fine without any type of misfiring, hesitation or leaning out problems and idles just fine.

awdorgtfo

iTrader: (17)

Front o2 could be bad

Spoolem

I was reading that you can test the front O2 sensor by unplugging the harness plug and disconnection the battery for about 10 min and reconnecting only the battery and driving it. If the problem is fixed then you know it's the O2 sensor.

Is this true??