O2 sensor reading RICH???

[Splorer Man]

hooked my 94 xplorer 4.0 up to a engine analyzer and didnt have any codes come up except the O2 sensor is reading rich.Would having a 180 t-stat instead of the 195 cause this??Or what might cause the rich reading??

 

[Glacier991]

What is the code you are getting?

 

[MrShorty]

I wouldn't expect a 180 t-stat to cause it to run rich enough to throw an O2 sensor code. Basic things that cause a rich code:
Bad electrical either in the O2 sensor or between the O2 sensor and the PCM
Fuel pressure too high
Leaking/stuck open injector(s)
Ruptured FPR diaphragm, allowing excess fuel to dump into the intake
I would recommend you get a hold of a proper EEC-IV diagnostic manual. Then you can read through the pinpoint test for the code you are getting and hopefully find the cause.