I have been tuning my LT-5 now that bigger exhaust cams have been installed.
Stock cams are 214d w .390". New exhaust is 220d w .425"
I'm using C/L but running into an issue of Left O2 Lean at idle. Coming up w a soft code which goes away once I hit the throttle. However, looking at the datalog, I can see that the left O2 transitions never exceed 64, while the right O2 terminate and loop back at 255. At the same time, I have been dealing w an IAC issue that I posted in a separate thread Disappearing IACs. I think I may have "fixed" that by tightening the clamps on the PCV inlet.
LT-5s generate a ton of vacuum. You can try putting a vinyl binder in front of the airhorn and it will literally rip the vinyl off the binder if you aren't careful. It puts a Dyson to shame. So vacuum leaks need to be tracked down.
Some additional info. Both O2s register .45v with key ON. Left bank runs typically leaner than right but the range of the O2 is smaller than the right side.
Motor idles between 875-925rpm which is expected. No surging at idle or any other time.
These are new Bosch O2s. I swapped them out w the cam change because I had previously seen what I thought was a lazy left O2. Perhaps it's something else.
Thoughts? Sensor ground?

 

I'm reading some other threads and they have caused me to recall some other details. In O/L warmup, both sensors will read rich as expected. C/L is when the left side stays pretty much under .45v. It also seems to be dropping out of C/L w extended idle. Sitting at idle is when I get the Code 64. Due to the cams, I have made changes to the O2 windows but only for idle by lowering the thresholds for idle airflow. Idle BLMs are 132/120 as an example. Cruise BLMs are tighter.

 

I dont know much about dual O2 systems but isnt the ECM supposed to switch banks frequently to develop accurate fuel trims? Maybe it isnt switching banks like it should and just using one O2?

 

Each bank has its own BLM/INT. In C/L , the injectors are being manipulated separately by bank to reach 128. However, each bank is working off the same VE table, so a large disparity may not be completely resolved. The VE becomes a bit of a compromise and larger cams have a way of magnifying that, particularly at idle. Since there are multiple cams, its very possible to have different cam timing left to right. in fact, even as delivered from the factory, cam timing could vary 3d +\- . Cruise proves to be not much of an issue as airflow becomes more consistent and pulses more rapid.

 

Is there an update rate seperately for L-R? Just a WAG.

 

Ronny,

I think I got the issue addressed. Installed a new O2 yesterday and I saw that it was switching unlike the previous sensor. However, my suspicion is that the sensor leads were tie wrapped to the clutch hydraulics SS line and that was attenuating the sensor ECM signal. It never got above .5v while at idle. Now it does.
However, the left side is still only showing up to 64 transitions. I thought I recalled modifying the ALDL to output another parameter as the Lft O2. Looking at the bin, it appears stock and not modified. Not sure what's doing on but I know O2 transitions ratchet to 255 before resetting.

 

Well no more SES light at idle, no Code 64. So at's solved. Also, solved the Xcounts issue. I was able to confirm that the ALDL was modified to so it reflected
Gms/sec rather than Xcounts. Keeping it that way because its good data to have.