General MTX-L Wideband always reads full lean

[Heat16]

Hey All I read a bunch of threads of people seeing similar issues with the MTX-L and other widebands, but none of the resolutions seem to be working for my setup.

Here's what's going on:
I have the MTX-L O2 sensor in the stock O2 sensor location.
I do NOT have a down pipe installed currently (the stock one is way rusted out and I wanted to get some other bits of the build sorted out before I purchases a new one).
I've done multiple free-air calibrations of the wideband as per the manual.
With the car idling (roughly, just got the new engine running two weeks ago) the Wideband is pegged at 22.4.
I also have it wired into pin 76 on my ECU and it's showing the same full lean results in ECMLink.

I've performed the following troubleshooting steps so far:
-Calibrated the Wideband multiple times.
-Unplugged the O2 sensor harness from the back of the gauge, turned the car on until i got an error code on the gauge, and then performed a calibration again
-Wrapped the O2 sensor in a towel with some brake cleaner (This actually gets the gauge to read values in the 10-14 range)
-Stuck the O2 sensor in the tail pipe of another running car (This also gets the gauge to read values in the 10-12 range)

For the life of me I cant figure out why when the sensor is screwed into my O2 housing, it reads full lean. I have a feeling that it has something to do with my lack of a down pipe and the sensor being in the stock location, relatively close to the open air. If that's the case though, I feel like sticking it in the tail pipe of another car shouldn't have worked?

Any suggestions are greatly appreciated.

Thanks!

 

[ChessmoDSM]

Sounds like you have a wiring issue, the location of the sensor should not have any bearing..

 

[Heat16]

I thought that at first too, but if it were a wiring issue, shouldn't it present the same issue when I stick the sensor in the tail pipe of the other car? Or when I wrapped it in a towel with brake clean?

A lot of other threads mentioned grounding issues. I currently have it ground to the back of the cigarette lighter, maybe the sensor is grounding when its screwed into the O2 Housing and there is something wonky going on between the engine ground and the cigarette lighter ground?

I'll try making a jumper and grounding it directly to the battery terminal.

 

[Dsm panda]

Could an exhaust leak pre o2 be causing it? I believe that's why mine is a - - at idle but once I drive it registers. (I'm missing a exhaust nut because I have yet to replace the stud)

 

[Vegas Smith]

Assuming there isn't a weird wiring issue (which is really common with these finicky things), it's probably the lack of downpipe. Your wideband is almost completely open to the atmosphere in that state. Connect the exhaust and I bet it will be fixed.

 

[19gsx91]

Alligatorrrrr clips are your friend for diagnosing possible bad ground/power signals.

Don't worry so much about getting it logging in ECMlink as making sure it's working properly in general, one step at a time. If you connect two small leads (power/ground) and connect them to the pos/neg wires on the wideband as long as it's plugged in it should read.. lock the car in closed loop and see where that lands you. It's never a good idea to "assume" any wiring is correct on cars of this age.

 

[donniekak]

With the sensor in the o2 housing and no downpipe you’re mixing free air with exhaust at idle.

 

[ChessmoDSM]

With the sensor in the o2 housing and no downpipe you’re mixing free air with exhaust at idle.

My tuner insisted on using the front 02 over the WB(no narrowband sim) for tuning purposes, can you educate me as to why the WB location being in front 02 location in this case would give incorrect readings? I am somewhat of a newbie and constantly adding "things to know" to my DSM bible, would appreciate your wiseman response..

Thanks!!

 

[Mello]

Because the downpipe is not installed. As the engine runs some outside air gets sucked back into the exhaust at idle & results in incorrect AFR readings. This phenomena falls under the category of overlap, reversion, scavaging.

 

[ChessmoDSM]

Fawk boys, I totally missed the part where he and the rest of you said he didn't have a DP(was on my stupid phone), please disregard my lack of eyeballs and carry on..

 

[donniekak]

Because the downpipe is not installed. As the engine runs some outside air gets sucked back into the exhaust at idle & results in incorrect AFR readings. This phenomena falls under the category of overlap, reversion, scavaging.

^^^^^^^^
What he said.

 

[red_devil]

Lack of dp may be the issue but just be warned those things are known for issues. Why I got rid of it after 2 years of issues and went with the new AEM x series.

 

[Heat16]

I suspected it might be the lack of downpipe, but the fact that it worked when I stuck it like 3 inches into the tail pipe of another idling car had me second guessing that notion.

As for getting the car in closed loop, I literally just got it together after building the engine and dropping it into a half disassembled car. It's gonna need a lot more love before it gets into closed loop idle, . I'm in the beginning stages of working the most basic of bugs out of everything (chasing down vacuum leaks, etc). Since I'm unsure of the car's history and everything, I don't really want to rev it out or even leave it to idle for too long without being able to check the AFR.

Either way I tried grounding it directly to the battery and now its throwing an E5 code which according to the manual calls for a replacement sensor. I tried recalibrating a few times and put it back the way it was (ground to cigarette lighter) and it wont move past the error code.

Now the real question is, do I bite the bullet and buy a new sensor, or scrap it all together and go with the AEM?

 

[motomattx]

AEM is not accurate the way the Innovate is, the AEM will just give you a false reading whereas the Innovate will flag a code if something is wrong, seems annoying from the Innovate, but I would rather have a known problem found during a self check than have false information propogated throughout my ecu and tune.

 

[red_devil]

AEM is not accurate the way the Innovate is, the AEM will just give you a false reading whereas the Innovate will flag a code if something is wrong, seems annoying from the Innovate, but I would rather have a known problem found during a self check than have false information propogated throughout my ecu and tune.

The old AEM used to be. The new X series are just as accurate and fast yet they are actually reliable and better made. They also log much better and can be recalibrated.

 

[Heat16]

Just for a bit of closure:

I ordered and installed a downpipe and the sensor is now reading values that make sense at idle.

 

[Dsm panda]

I fixed mine by moving my wb to the factory o2 sensor spot and now mine reads correct. It was just before the flex pipe.