No O2 - how much does it affect the mileage? (1 Viewer)

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Just bought a 92 FJ80, 3fe to park next to my 40.

The only codes thrown are for O2 issues. Someone has removed the cats while messing with the rest of the exhaust. I've only been under it for a few minutes looking, but did notice that what I assume is the O2 connector is just hanging from the harness, no O2 sensor to be found, hanging or installed. No bung either.

So. Covid shutting things down, I got this truck for a work trip that starts in 2 weeks. Registration is going to be difficult, I need to rebuild the birf's for peace of mind, bleed the brakes, and a few other things, so time is a little busy right now. How much does the stock computer over fuel before leaning on the output of the O2 sensor correction? I have the ability to to fix this issue, just trying to prioritize things. Also, how much is that over fueling compensated by E10 fuel?

I have no tags on it yet, so I can not go out and even get a baseline MPG just yet. Engine does seem very strong and happy with the way it is right now.
 
My '94 had O2 issues for months. There was no measurable difference in fuel consumption that I could see. Engine was strong with or without the CEL. I know I have a different engine so things might be a little different for the 3FE.
 
same with my 94 also,cel and bad o2 sensor,still got a whopping 10.5 mpg,now my 06 durango popped a bad o2 sensor code and mileage went from 16mpg in town down to 11mpg
 
I have the same issue. I also have a 92 with a 3FE. Previous owner installed a new exhaust and never bothered to install the O2 sensors.
I have a constant check engine light on but the engine runs fine. I get between 10-12 MPG with the CEL on.
I've been told even with O2 sensor working properly the fuel mileage would not be much better.
It's low on my to do list, but if I ever do fix it, I'll do it with O2 sensors installed. I would be curios on if anyone else has info on this.
 
That is at least a little confidence, thanks everyone. It should run rich as a default safety factor, but that was before 10% ethanol in the fuel.

It stays on my list, but will not be the top most priority.
 
you may see a light drop in mpg compaired to what you would see with the o2 sensors, but itll run just fine. id do something to seal up the connectors on the harness to prevent corrosion if the pins aren't green yet and your planning on putting the sensors back in again. any exhaust shop will be able to cut and weld in new bungs for you for fairly cheep
 

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