You had an O2 sensor w a connector not completely seated. The O2 sensor is a 3 wire installed in the collector of a right side header. The BLMs on the right side are consistently richer than the left.

 

Well I went through the work of removing the right side O2 harness extension and actually built a new one. There didn't seem to be much wrong with the original one but it had been there for several years and I thought what the heck. Made certain that this time the harness connector clicked shut.
Got everything buttoned up and took it out for a logging session. Along w that I dropped the Injector Bias considerably and back to a previous set of VE tables.
The BLMs were much better and tracked very closely to each other. Much smoother drive although I still saw points where it would drop out of C/L. Viewing the log, some of those times, MAP was below the threshold for C/L.
Also, the right side still has frames where the O2 signal drops to 0. In the log, nothing changes that I can see. It will stay in C/L and Learn. I don't feel anything while driving. AE needs to be addressed. If I am lowering the VE in certain parts of the table because the injector is now effectively providing same fuel at smaller PW, is the AE too large. It happened much less frequently w this latest IB change, but I still got one or two instances on the WB of the AFR going rich, then lean when pumpshot came in. Since AE in the LT-5 works on delta MAP, even a steady throttle can bring on additional fuel.
So unless I just have a flaky O2, not sure how to explain the signal drop out.
Left side shows no sign of that although both sides do track w each other. It's just that one drops to 0 and the other does not.

 

I thought you swapped 02's L-R R-L to prove one was not flaky?

I thought you were going to state you had it fiquered out?

I hope you have a heated garage!

Bears gonna win tonight?

 

Ron,

I had switched O2s some time ago when I was dealing w a Lean O2 issue on the left bank. That turned out to be a change in the calibration. Because I have larger cams, I had lowered the idle O2 window and effectively was forcing the ECM to go lean. The right side was ok but I assume there's enough variability in the O2 sensors themselves to where the right side was ok, but the left was lean.
So I was getting a Lean O2 code. Not sure if it's the same in other cals, but in the LT-5, if the O2 voltage is below .2v for 50sec, it throws a code. By raising the window above the .2v threshold, problem solved.
In another thread, I've been playing w the Injector Bias because of the Accels that I installed. These are not the original and unfortunately ACCEL doesn't make available the Voltage Bias for their injectors, unlike other sources. My VE tables have the telltale "bathtub" that can be indicative of incorrect IB values. So I have been datalogging various alternative IB schemes. Reviewing the logs, I noticed that the right side O2 would either drop the signal or go to 0. Very intermittent. Couldn't spot a pattern or a something that would precede it. Because of the signal loss, I suspected perhaps a connection and redid the extension harness for the headers. Took the car out, and the calibration was almost perfect. It ran great. Made a few changes to the cal and tweaked the VE.
Downloaded it to the Ostrich, As the motor warmed up, right side went very rich.
Backtracking now.

 

So the latest is this. I made a new harness extension for the right bank O2. Took the car out for a run to datalog and it ran very well. Looked as tho I had gotten the IB much closer and the R/L BLMs tracked much closer to each other
which helps in keeping VE changes less radical. So I load up the new bin w tweaks in the VE table based on the previous datalog. Motor warms up, but it goes Closed Loop and starts to stumble. My WB, which is on the right bank, shows that side going VERY LEAN. I did a log today in the garage and it shows

1. R/S O2 starts out at 1.1v. Didn't know it could go that high.

2. As the motor warms up, I can see L/S O2 voltage dropping while R/S stays at
1.09v

3. The log shows the R/S Injector PW dropping way below L/S which confirms what I am seeing w the WB.

4. I had scanned O2 voltage w Key ON/Motor OFF and it reads .45v

I guess my first move is to replace the O2. Why it would go so flaky so quickly
is a mystery to me right now. I may need to go back to the harness extension if this doesn't do it but there is no code thrown other than Rich O2 R/S. Looks to me that ECM and Injectors are doing what they should do given the data.

 

Swapped in new O2 and got same result. Next step is inspecting the harness extension again.

 

Dredded exhaust leak ??

 

No sign of one. And the car ran great just after I had installed the new harness extension. The next day when I re-start the motor, I get this issue. Crawling under the car today to check the harness again.

 

Well I'm a bit baffled right now. Pulled the extension harness and it tested fine with ohmmeter. Twisted, turned, no problem. What's happening is that the R/S O2 will show 1.1v with engine running. As it warms up, the volts do not drop unlike the left which does. This causes the ECM TO "think" it's rich and so it reduces fuel. The service manual call to disconnect harness from O2 and jumper the harness connector O2 signal to ground. This should then display on scan tool at < .350v. If not, then replace ECM. Its not clear that the test is run with key ON, OR Engine RUN. WITH KEY ON, it remains at .45v. I swapped in a new ECM, a different prom, still no change. Also, O2 sensor voltage should not be > 1.0v.
Am I getting power leak from O2 heater element circuit? Any suggestions are much appreciated.

 

Check that the ground input to the ECM for that O2 sensor is OK. The O2 amplifier in the ECM is a differential amp, and requires a good ground input. Same for the O2 sensor itself, a 3-wire sensor grounds the signal via the sensor body, then through the exhaust to finally the engine block.

RBob.

 

RBob,

Here's a summary of what I did yesterday.
I must be doing something wrong. The FSM calls for me to ground the O2 sensor signal line. It should drop below .35v. Do I do this while running the motor or just w key ON? With key ON, I get no change in the O2 signal voltage. It remains at .45v for both sides. Swapped both prom and ECM. Same result.
Also checked for continuity on O2 sensor ground and signal lines. Both tested good while twisting and turning harnesses. W new ECM, I did run the motor and still ended up w 1.1v on signal circuit. Makes me think I have an extra power signal showing up. Think I may pop the ECM O2 signal connector, then turn on motor and see if I still get a signal. Does O2 heater circuit come on w key ON, OR w Engine Start? Right now I'm slightly baffled. It'll probably be something really stupid. Occam's Razor.

 

Most likely need the engine running. Some masks read the O2 with just key-on, but will still init the O2 value to 450 mV on a regular basis. With the input grounded to the ECM I would imagine that the value would be very close to 0 volts.

Not sure when the heater is powered. Sometimes GM will use the fuel pump signal to power the heater.

RBob.

 

RBob,

So here's an update.

Well I got it working today. Ran a few more diagnostic tests after reinstalling O2 sensor ground line in ECM.

1. Unplugged A/C fuse to eliminate any possible "crosstalk" from the heater circuit. Both O2s remained at .45v after engine START.

2. Reinstalled fuse, disconnected O2 and jumpered the O2 signal to ground. Engine needs to be running otherwise it will always show the ECM bias value. This dropped the R/S O2 to .03v so that was good.

3. Tried both harness extensions I had. The one I made the other day appeared to be giving me a problem. So I made one more extension and installed it. Now it appears to be working altho the O2 will jump in and out of Closed Loop if CTS isn't above 77C. Fans kick on and drop coolant temps in this weather. Just need to get heat into motor. Hope to take it out tomorrow and do some logs
but looking at idle the O2 voltage seemed to be tracking closely along w INT. Right was somewhat richer than left as usual.

I look forward to viewing the logs and seeing how close the BLMs are. Also want to see if I get any dropouts in the O2 signal.

Keep you posted.

 

Done 2 runs w the new extension harness, and motor seems to be running real well. Whatever I did worked, including eliminating the O2 sensor signal drop I had on the Right Bank. No loss of signal now. However, I am getting a C/L to O/L to C/L flip flop at times. The hotter the CTS the less it happens but looking at the logs, my best guess is that I am hitting the top or bottom of the C/L O2 window.
That's what seems to be going on. Should I leave them alone or increase the spread? Right now its stock at .698v/.198v. Its seems to be more frequent w cooler MAT/IAT temps.
Maybe run less Prop Gain?

 

try to tighten up the gap for the swing point qualifier. shouldn't drop out of CL after that.

 

You talking about R/M/L windows or the C/L O2 window?

 

The C/L window. I had a similar problem in my car after I tightened up the R/M/L tables, during really light loads and engine speeds ~3K it would fall out of CL.

 

Thx, any advice on how much to try?

 

since I have an emulator my practice isn't as exact as some, but if it were me i'd try 100mV narrower. so ~ .250/.650 and see what happens.

 

There's one issue with that. I have lowered my O2 R/M/L at idle to accommodate the larger intake and exhaust cams I installed earlier this year. As I continued to tune, the tune got leaner which ultimately triggered a Code 44, Lean Left O2.
I finally realized that I was forcing the ECM to target an AFR that took me below the C/L Window. Once I raised the R/M/L for <16gm/sec., problem solved. Narrowing the C/L Window, I'll need to. I've the R/M/L as well. May give it a shot but I may play w the Prop Gain so perhaps I don't get as much of a swing either.