Tuning question - Downstream 02 sensors in/out of exhaust

[stansfield187]

I just had my truck tuned and the dowstream o2 sensors are disabled. I unplugged them and installed fittings for my bungs. The truck ran like crap afterwards. I called my tuner and he said on some vehicles it needs to be plugged in, and I can zip-tie the sensors somewhere. So I plugged them back in zipped tied them. It runs better but I still notice a couple hiccups. I came across a thread in another forum that the downstreams need to be plugged in, but it didn't specify whether they need to be in the exhaust. Do they still need to be in the exchaust for heat? I'm not running meows. Thanks

 

[DILLIGAF]

Mine are plug in where they should be. But the 02 code is disabled in HP Tuner

 

[pacofortacos]

I have used these and can't say enough good about them - other than the price.

O2 Simulator Mini Cat Cel Fix stainless steel Rear O2 sensor simulator.

O2 Simulator Mini Cat Cel Fix, Big Daddies Garage Mini Catalytic Convertor Rear Oxygen Sensor Simulator is the best and easiestway to clear p0420 / p0430 codes for bad or missing catalytic converters. Just screw it the o2 simulator mini cat into the existing exhaust then srew in the oxygen...

www.bigdaddiesgarage.com

I used them with active rear 02 sensors and they still worked perfectly.
Tried the antifouler trick and while it did work, they only lasted a few months in winter salt.

 

[danielmid]

If the tuner disabled the input from them it has absolutely no side effects to put them back in place in the exhaust.

 

[DILLIGAF]

I have used these and can't say enough good about them -

Hes already tuned it would be useless.

 

[stansfield187]

I found an interesting post that the rear o2's play a part in long term fuel mapping. I will put them back in the exhaust tomorrow. I removed them after the tune because my exhaust was leaking from using spark plug anti foulers.

 

[pacofortacos]

Hes already tuned it would be useless.

I realize that, however he says they do appear to be affecting the running of the truck.
Maybe the fault code is turned off but the sensors are still active in the tune?
Especially if the tuner is telling him they may need to be plugged in - if they were tuned out completely it shouldn't matter if they were plugged in or not I would think.

 

[Sillygoose]

I found an interesting post that the rear o2's play a part in long term fuel mapping. I will put them back in the exhaust tomorrow. I removed them after the tune because my exhaust was leaking from using spark plug anti foulers.

i always thought the rears were for monitoring cat efficiency and nothing more. curious to hear otherwise

 

[DILLIGAF]

Maybe the fault code is turned off but the sensors are still active in the tune?

Thats not how tunes work, and rear 02 have nothing to do with mapping. Thats why we install an AFR gauge with 02 Sensor installed in the collector.

When you do your log file it clearly shows you Air fuel ratio.

 

[Sherman Bird]

I just had my truck tuned and the dowstream o2 sensors are disabled. I unplugged them and installed fittings for my bungs. The truck ran like crap afterwards. I called my tuner and he said on some vehicles it needs to be plugged in, and I can zip-tie the sensors somewhere. So I plugged them back in zipped tied them. It runs better but I still notice a couple hiccups. I came across a thread in another forum that the downstreams need to be plugged in, but it didn't specify whether they need to be in the exhaust. Do they still need to be in the exchaust for heat? I'm not running meows. Thanks

"Same load, same fuel, same air". The computer is almost ALWAYS seeking Stoic. Period. Regardless of manufacturer. 14.7 to 1 is lambda, stoic, ideal air fuel ratio. And, this is true at all but WOT operation!
So... the concept of leaving the rear sensors out of the equation is what? They play a part is fuel control. If the new "tuner" program files exclude them, then the question I'd have is why?

At WOT, the rear sensors do nothing anyway. The Air/fuel ratio is about 12 to 1 in most instances and the computer ignores finer engine management concerns.

 

[stansfield187]

Sherman, thats kind of what I was reading on a Ford SVT forum while digging around for info. But - apple and oranges - the svt's in the comparison were using wideband upstream and narrow band downstream. The narrowband downstreams calibrated the wideband upstream. I think on another Ram forum a user mentioned the rears playing a part in LTFM -possibly same concept. I can tell it's throwing codes because my MDS stops working on the codes. I hope I don't have to run anti foulers again because they leak. I wasn't around when my truck was tuned. I couldn't afford a dyno tune at the time. I'll eventually go back to them when I have the coin.

 

[Wild one]

Sherman, thats kind of what I was reading on a Ford SVT forum while digging around for info. But - apple and oranges - the svt's in the comparison were using wideband upstream and narrow band downstream. The narrowband downstreams calibrated the wideband upstream. I think on another Ram forum a user mentioned the rears playing a part in LTFM -possibly same concept. I can tell it's throwing codes because my MDS stops working on the codes. I hope I don't have to run anti foulers again because they leak. I wasn't around when my truck was tuned. I couldn't afford a dyno tune at the time. I'll eventually go back to them when I have the coin.

Where are you buying your anti-foulers at? I run anti-foulers under the back 02's on my toys,and i've never had one leak yet.These are what i have under the rear 02's on both the car and the truck.Run a tap through the holes,to clean up the threads,and use a bit of high heat anti-seaze on the threads when you screw the anti-foulers in place and a bit on the O2's to,just don't get any on the sensor part of the O2.

https://www.amazon.ca/Eliminator-Adapter-Adapater-Isolator-Extension/dp/B07NVMRT2N/ref=sr_1_4?crid=23NQW1PXX376Q&keywords=2pcs+O2+Sensor+Spacer%2C+Keenso+M18*1.5+Check+Engine

 

[stansfield187]

These were cheap aluminum from O'reillys. I think the threads on one of my bungs is gimped. I also think I stripped the threads on the left side anti fouler. I should have ran anti-seize. Oh well.

So, I put the O2's back in my exhaust and still ran like crap - UNTIL I reset the PCM and did a few drives and cranks. I did not reset my PCM through testing after I unplugged the O2's. Runs like a kitten purring on a silk blanket. I thought the computer would see the corrections and be happy. I guess negligence on my part. I guess the verdict is still out there if we can totally remove them, because I'm not playing with them anymore.

 

[Wild one]

These were cheap aluminum from O'reillys. I think the threads on one of my bungs is gimped. I also think I stripped the threads on the left side anti fouler. I should have ran anti-seize. Oh well.

So, I put the O2's back in my exhaust and still ran like crap - UNTIL I reset the PCM and did a few drives and cranks. I did not reset my PCM through testing after I unplugged the O2's. Runs like a kitten purring on a silk blanket. I thought the computer would see the corrections and be happy. I guess negligence on my part. I guess the verdict is still out there if we can totally remove them, because I'm not playing with them anymore.

Sometimes you can get away with leaving them out of the exhaust,but usually they still have to be plugged in.

 

[pacofortacos]

Why do they still have to be plugged in if the tune totally eliminates their input as Dilligaf implies?
I always thought the rear O2 was just a cat efficiency, but others have stated that it does trim the fuel a bit - I haven't seen the OEM programming to see if it does or doesn't.
Or
Do they have to be plugged in just for the heater voltage half?
And do all tuners/tunes ignore the sensor or just ignore the fault that would be generated.

Maybe the fault code is turned off but the sensors are still active in the tune?

Thats not how tunes work, and rear 02 have nothing to do with mapping. Thats why we install an AFR gauge with 02 Sensor installed in the collector.

When you do your log file it clearly shows you Air fuel ratio.