Ok, so I'm trying to figure out what May or may not be an o2 sensor problem.

Here's the deal.

NO CEL. No pending codes. I have two ultra gauge alarms. Cat bank 1 sensor 1 value 8799 max alarm value 2011. Second one: long fuel trim bank 2 value -0.8 alarm min 10.0.

There is also an error showing that it is running in open loop.

Mileage is atrocious, you can watch the gas gauge go down as you drive.

More info - three years ago I welded in new generic cats and replaced all four o2 sensors. The welds left a little to be desired quality wise as all I had to work with was a crappy harbor freight single phase welder and flux core. All four joints leak, but not majorly.

I have procured a used but good condition y pipe and want to put it right. My first instinct is to replace the o2 sensors, but I hate to spend the money unless absolutely necessary. Three years seems pretty short for the lifespan on the o2s.

Any insight on what this all could mean is greatly appreciated.

 

I'll be interested to see how this comes out as I too have terrible mileage and no cel but I a also do not have a scan gage. By terrible I mean about 160-180 miles on a tank of 90. The only not stock option are the 245/75/16s

 

Same here,:
i got like 10/10.5 MPG last tank super

 

Ok so I figures there wouldn't be much response to this, so I am just going to keep this updated to help anyone dealing with the same issues.

Got the old leaky y pipe out today. Decided not to order o2s until I was sure they are needed. Cleaned the o2s with electromotive cleaner and a ton of carbon came out of the fronts when I blew them out with air. Backs were pretty clean. Swapped sides with the fronts just to see if the issue will travel with the sensors.

Put the new pipe in and wow! What a difference noise wise. It is so quiet now without all the exhaust leaks that I can now hear all matter of rattles etc in the cabin that need attention. Gotta get on that.

Programmed the ultra gauge for the o2 sensors. Voltages and short term fuel trim seem about right. Voltages bounce around 1 to 2, but more importantly they seem to be more or less equal, same for the short term trims, bounce around 1-8 or nine, but mostly equal. They go negative when I jump on it or starting out from a dead stop.

One thing that puzzles me is both sides present a long term trim value of zero. Will keep an eye on that as miles accumulate. Will also see if mileage improves.

 

Found this thread on a search...are all four sensors the same, or are they all different, or are some the same (i.e. uppers versus lowers, or right versus left, or?). My CEL has been on for about a month now, mileage has dropped from around 15+ to 13+, so something's going on. It's at the shop right now, I just want to know if these sensors are all the same, or are all different, or? I'm sure I can get the sensors cheaper myself, just need to know if they're all the same or different.

 

Might try cleaning the MAF sensor with MAF cleaner.

 

So geek how's your mileage doing?