All 4 O2 sensor burnt, Fr/Back Cat conv/mufflor rusted out in one year.

[chirozapo]

Hi there, I am new to the forum. I bought a 97 QX4 second hand from private seller 3 years ago. The CEL was on when I bought it but the seller told me he had all 4 O2 sensor changed but didn't reset the computer ( a lie). After I bought it, took it to a mechanic and was told all 4 fail so had them all replaced w/ universal type. CEL came on after only 30minutes of driving. Burnt again!! I also had front and back Cat Conv/ muffler changed about 2 year ago, and it's rusted out even the exhaust tip fell off!! I have been reading the forum and sounds like a moisture on O2 sensor prob but also could be a faulty ECU. My dilemma is if I spend $800 replacing all 4 O2 sensors, and turned out to be a bad ECU then I end up losing $800. Found a used ECU on Ebay for $99 and bought it. Can anyone give me some suggestion? Any experience with that? My current mechanic guy thinks it can be because of the universal o2 sensor not being a fit to OEM specs, but I don't really think that's a problem. Thanks.

[Buzzman]

My current mechanic guy thinks it can be because of the universal o2 sensor not being a fit to OEM specs

After hearing and reading about the 02 sensor issues for the past year and a half, I tend to agree. Go OEM.