O2 Sensor replacement
I'm not as technical as most of you guys that are active posters on the forum, nor have I done as much DIY work on my truck, so bear with me.
I have heard many of you talk about the possibility of a bad O2 Sensor being the cause of poor engine performance, poor fuel efficiency, etc. I have never replaced one, and don't even know it's location, but do understand the basic principle of its purpose.
I have for some time experienced poor gas mileage and it also seems that I have to push the engine harder for it to perform day to day as it used to. I have been through many things in my head that may cause this: filthy TB (has been cleaned), dirty MAF (cleaned, water in gas (added seafoam, actually to crankcase and gas tank), and a number of other things.
My question, how would I know if the O2 sensor is bad? I know it would throw a code, and it hasn't yet, but what's the possibility that it's going bad and hasn't thrown any codes? I guess it is still possible that there is a problem with the cylinder heads, but the dealer won't do a compression test on them unless the CEL comes on, and even then, being out of warranty, it would probably still cost me.
Any thoughts from anyone? I'm at a loss here and don't know what to do next. The dealer is increasingly uncooperative. Should I just pay for the compression test? Should they be doing that for free since the symptoms could be related to the head issue? Also, what's your dealer usually charge for diagnostics? Mine wants 95 bucks!!!!