AEM AEM Wideband shows full lean after engine warming up, engine acts normal

[patman]

Hi guys!

So I got my car out of winter storage for a month now, and after a few drives, I noticed my wideband is showing full lean (- - -) all the time I am driving, after the engines warm.

It settles at 14.7 during warmup, and even after that, the engine acts normal, (I have stable idle, engine pulls great, no weird smells) but the wideband just goes full lean. A changed the sensor, but it's still the same. Anyone knows what I should check next? Maybe it's the AEM meter that's gone?

 

[chrysler kid]

could you have an exhaust leak? or the exhaust bung could be cracked?

 

[patman]

I checked it. My downpipe gasket was a bit damaged, so I added a healthy amout of exhaust sealant cement there. No other leaks on the way to the O2 sensor

 

[dwb]

Have you tried an open-air calibration?

 

[patman]

No, I'll take a look at that this weekend

 

[jed344]

Sound like a wide band issue. Do you have a factory front o2?, if so in the log when the wide band goes full lean what does stock front o2 do?

 

[curt-s]

Sounds like your wbo2 isn't providing closed loop operation for you as if it would be throwing off your trims wildly, so we'll take it as just a diagnostic device and you have a factory narrowband in the o2 housing.

I had an issue years back when it was cold/warming up, I'd get perfectly normal WBo2. But as everything warmed up and especially after driving, I'd go lean a full point or more. Once there was sufficient heat in the exhaust, gaps opened up between the O2 housing and downpipe, allowing oxygen in during cruise. After a while, it blew the gasket in two.
A tiny leak that wasn't even audible, but it was enough to mess everything up & destroy a composite graphite gasket.

 

[Jk's97DSM]

These wideband sensors are notorious for giving out after sitting or not being used because of condensation building on the sensor.

 

[curt-s]

Which AEM? LSU 4.2 or 4.9?
Installed at a min 30 degree angle?

"These wideband sensors" -- which are you referring to?

 

[Jk's97DSM]

Bosch widebands in general. There has been lots of issues over the years.

 

[curt-s]

Yeah well when you produce the vast majority of the oxygen sensors as an OEM for a billion cars.. there's bound to be a LOT of complaints whilst still remaining under a 0.1% failure rate.
The same fact is most modded cars use Bosch sensors just fine, including mine which sits for 7 months of the year.
I read about a lot of AEM issues, more than Innovate, but either are probably still good even today.

 

[patman]

Thanks for the replies guys. It's a Bosch 4.9, and as I mentioned I just changed it, so I think the sensor is ok. I think it takes information from the front O2 (narrowband). I'll do a quick cruise and try to catch as much information as I can, and in the weekend, I will take the downpipe off and look out for any pinholes. I dont think the gasket is the culprit, I sealed it with a handful if exhaust sealant cement, but the downpipe is OEM, so there can be small hole at the resonator or at the bung.

I will post an update after I find out more

 

[patman]

So I did a longer drive this weekend, ready to log the issue, and the car maigcally fixed itself, It didn't lean out during a 2.5 hour long drive. I had new FIC 850s ready to install when I got back, so I changed that, and started to adjust my mafcomp, and it still runs like nothing happened. Maybe a sealing needed to settle in place somewhere, or the sensor had some issue, but it seems to have fixed itself now, I'll keep checking it.

Ps.: Now my AEM gauge is starting to act weird. The LED sections are burning out, one after another (now 3 sections are burned out on the last digit, so it's impossible to tell if it shows a 14,7, a 14,1, or a 14,9) or it's just hard to figure out anything :/ Did anyone had the same issue? Is there a way to fix the LED burnout? I was trying to look for a teardown guide, but haven't found anything yet.