No O2 sensors

[Dave1x1]

I,m removing the cats and running the exhaust inside the frame rails on my 88 FJ62. The muffler shop didnt have the right bungs for the Toyota sensors. So they are going to setup the exhaust now without O2 sensors. Besides a check engine light, what problems will this cause temporarily? Aren't they just thermal sensors? They don't actually control the fuel mixture in these engines do they?

Thanks!

 

[billmc]

(even more) terrible gas mileage. Yes, they control fuel mixture most of the time.

 

[Dave1x1]

Will is just affect until the engine is warm and the sensors would normally heat up?

Also, the shop only has the standard bungs, is there a compatible sensor that will work with standard bungs on the 3FE?

 

[3_puppies]

aside from breaking federal law,

could they cut the originals off and re-use them?

 

[Dave1x1]

I just ordered the bungs from Slee. Not too cheap, but at least it will run correctly now. I'll just have the shop go back and weld these in when they come in.

 

[billmc]

Will is just affect until the engine is warm and the sensors would normally heat up?
QUOTE]

Not sure I understand your question. 3FE O2 sensors are three-wire which have their own heating element to heat them up faster. O2 sensors are almost always involved in the ECU's mixture calcs. What sensors are you talking about heating up, since you're talking about running O2 sensor-less?

Bill

 

[Dave1x1]

It's probably because I'm not entirely sure of what I was asking. My thought process was that since these engines are relatively simple, that the O2 sensors were only used to monitor engine controls if the engine temp varied greatly, either too hot or cold. Otherwise, when the engine is a normal operating temp, there wouldn't be very much for the sensors to monitor.

 

[billmc]

It's probably because I'm not entirely sure of what I was asking. My thought process was that since these engines are relatively simple, that the O2 sensors were only used to monitor engine controls if the engine temp varied greatly, either too hot or cold. Otherwise, when the engine is a normal operating temp, there wouldn't be very much for the sensors to monitor.

Simple relative to what? I think you've got it kind of backwards. For a properly running engine, warmed up, I'll guess that above 1500 rpm it's tuning the mix almost solely based on the O2 sensors, using the other sensors such as the AFM, TPS, RPM, etc., mainly as data consistency checks. It will run in open loop without the O2 sensors, but in a much cruder fashion. I'm not a Toyota engineer, and have never seen a reverse-engineered spec of the ECU, but that'd be my guess.

Bill

 

[billmc]

btw - when your guys put your new system back together with the sensors, make sure they associate each sensor with the correct bank of cylinders. It's important.

 

[disassociative]

Agree with everything Bill said, the O2 sensors are important for fuel mixture. You'll likely be running rich without them, which will make you stinky as well as shorten the life on many of your FI and exhaust components.

As for O2 sensor compatibility, there are plenty that don't use the stock Toyota bung. Check out Rock Auto for some options.

 

[Wile E Coyote]

I'm glad your gonna do it the right way.
What kinda muffler shop would agree to not running O2 sensors? Also, they would have to know that as pointed out, there are several universal sensor options that don't need the Toyota flange.

 

[Dave1x1]

Bill,

And everyone, Thanks. Once again Mud proved its worth!

In my research, I did find a post that described which sensor went with each bank. I'll need to bookmark that when I find it again. From what I remember, exact distance from the manifold isn't crucial. As long as it is upstream from the converter location.

By simple, I think I meant OBDI vs OBDII.

 

[disassociative]

Bill,
In my research, I did find a post that described which sensor went with each bank. I'll need to bookmark that when I find it again. From what I remember, exact distance from the manifold isn't crucial. As long as it is upstream from the converter location.

I was totally geeking out about this last night: https://forum.ih8mud.com/60-series-wagons/590671-oxygen-sensor.html

Distance shouldn't matter too much, unless you're under water and the pipes get cold. But as Bill points out, you'd do well to match the cylinder banks.

 

[snowakii]

Distance won't matter, but switching them will. The shop that did my exhaust (moving the cats inside the rails) swithed the two. Very poor warm performance and gross poluter at smog check time. The computer was always confused until they were switched back. In my case, due to where the bungs were located, swapped the wires for the two o2 sensors at the computer... when I can get the o2 sensors themselves relocated I'll swaep the wires back. Smog check was VERY clean. Don't know where the test results are, so please don't ask.

 

[Bowling4$]

I learned the importance of the O2 sensor the hard way. After rebuilding my motor I reused the old rusty sensors. I started the vehicle and had fuel pouring out the exhaust. I drilled down which pipe it was going down and decided it must be a stuck fuel injector ended up removing and replacing 3 injectors each time only to find out that it wasn't the culprit. Obviously it was the o2 sensor. Expensive and timely mistake. Keep the o2 sensor if you want to run fuel injection. Just my 2 cents.

 

[Dave1x1]

Well. The exhaust is finished and looks pretty good. It's nice to have everything tucked up inside the frame rail. I'm waiting on the new bungs to get here, but in the meantime I'm driving the thing everyday and it has yet to trigger the CEL. I also haven't noticed any strong fuel smell in the exhaust or terrible mileage yet. I'll monitor this tank of gas to see if it decreases noticeably.
Thanks again for the assistance!