I'm about to part this out... I can not figure it out..

Constant 'lean' from one of the o2 censors. Floods the engine at idle so bad that its unbearable.

Going down the road, (when not using the o2 I guess) works the very best... but the sitting in traffic is not a very pleasant experience.

Tried multiple o2 sensors, both ACDelco and off brands, no change. had wires traced back to ecm, no issues with continuity or anything like that.

Checked pins on the ECM, all good, nothing showing any alarms there either.

so, I'm reaching out to the group, has someone, ANYONE, ever come across this before? I truly need to get this running correctly.

Engine build is in my signature, initial tune from Solomon @ LT1 PCM Tuning - Welcome! is in the car... he couldn't help any more because of the constant lean coming from the o2 sensor.

Truly appreciate any and all constructive insight and suggestions.

Brian

 

Did you check the O2 sensor heater wires? They don’t connect to the PCM. There's a 12 volt wire and a ground wire. If one of the sensing element pins or wires was shorted to ground within the harness connector, it might result in a constant 0 volts (lean) at the sensor.

The PCM supplies ~0.450 DC volts reference to the sensing element wires. Key on, harness disconnected from the sensor, check the DC voltage across the two sensing element wires. You need to use a very high impedance volt meter to avoid damaging the PCM, and the actual voltage measurement could be off by +/- 0.100 volts and still be good. What you are looking for is a near 0 volt reading, indicating a problem

http://shbox.com/1/HO2S_connector.jpg

Have you checked for misfire on one cylinder in the bank that has the lean reading? If one injector is plugged, all the air compressed in that cylinder flows into the engine exhaust, causing the O2 sensor reading to show lean. Ditto with a misfiring plug. Unused air blows out into the exhaust and produces a lean reading.

Has Solomon already made any of these suggestions? Did he mention that your huge cam overlap can be dumping air into the exhaust at idle (not sure why it would only affect one bank - but I'm not a tuner). Did he compensate for that in the tune?

 

Thank you for the reply, it is truly appreciated.

I'd like to state, Solomon has been a great guy to work with... This build has been years going back and forth with him on all this, but we haven't been able to sort anything out.

Secondly, shbox has been my bible, if bibles came as picture books...

Maybe I'm not following exactly what you are saying, but tomorrow will be round 200 of this peck and find with this problem. I own the following meter, has been rock solid for me for years. In case the link won't work through the forum, it's a UEI DL99 unit.

https://www.platt.com/platt-electric...px?zpid=195780

Your opinion, would this be sufficient to test what you are referring to in your reply? If not, I can track down an 'elec-chicken' I know and borrow one of his more expensive meters. What I am understanding is I should test between Tan/Wht and Ppl/Wht on one side, and Tan and Ppl on the other... anything better than zero is a good harness to PCM connection?

Then the Brn/Blk can be tested for 12 volt across those two pair without having to worry about the PCM. Again, not looking for a zero read here either.

Thanks for the advise, 11 years being on here, have had a couple scammers, but for the vast majority of the time, it's been a great experience thanks to folks like yourself.

 

Generally, digital volt meters are very high impedance. Only analog meters are a concern. The literature I've seen with regard to measuring the O2 sensor circuit indicates a 50 Kohm minimum. I think modern digital meters are typically 1 megohm. I don't see that data in the link, or in the “catalog page” linked in the link. Disclaimer - I am a mechanical engineer, not an electrical engineer.

How have you determined the O2 sensor is stuck in the lean condition? Do you have access to a real-time PCM scanner for checking the sensor readings? A “stuck” sensor will set a code as well in closed loop.

Another item I remembered - high high voltage wire running in parallel with the sensor wire, like a plug wire can affect the voltage readings.

Since you have tried multiple O2 sensors, now look specifically at the harness side connector. You want to insure there is no current flow between the sensing element wires and the heater wires. Test resistance between tan/white wire and each brown wire, one at a time. You want infinite resistance. Repeat between the purple/white wire and each brown wire. Do this first with the connector unplugged. If infinite resistance in all cases, insert the sensor plug into the harness and see if you can run the same checks. Access will be difficult, but sometimes a straight pin works. Just looking for an outside chance that plugging in the sensor shifts the harness connector pins and causes a “short”. Seems overly cautious, but you've tried everything else.

 

No luck, everything pins out just fine... so at this point, it has to be the PCM I think? I have a couple more lying around... will need to setup a new machine to get my tunercats to connect as well... took all day yesterday and a little time this AM to locate my ALDL cable...

 

No plugged injector(s)?

Could you provide an answer as to how you determined the O2 sensor was reading lean, from post #4? Have you looked at the long term fuel corrections for all 18 cells?

 

I was in the middle of restoring my virtual machine, which should contain the data logging I did previously... then my hard disk died.

I've just returned from getting a new disk this evening, and should have the computer operation later tonight.

 

well, as luck would have it... I don't have the data log files.

I DO have all my tune files,... I went in to have a look...

I could, in the ECM switch table, remove the one troubled O2 sensor side, and just rely on the other maybe? outside of this, I think I need to find my spare PCMs and try another one.

It's too late to go for a drive now, I'm planing a lunch hour rip with a data logger tomorrow to confirm what I had prev stated.

Cheers,

Brian

 

another update...

So, my odb cable no longer works apparently... just bought another, waiting for delivery... - What do you think about the idea of shutting off that one O2 in the PCM? If the car runs correctly without it, and all wires and that sensor have tested good, that has to point to a bad PCM right?

 

The whole process becomes much more visible with a correctly run data log.

On the other hand, I have no idea what happens to the closed loop A/F ratio control process when you turn off one of the O2 sensors. In fact I don’t know how you do that.

 

you need to listen to "Injuneer" and run a proper data log.
instead of throwing parts at it!

 

Oh I'll be doing exactly what he's suggested. No question there. The new ALDL cable should be here any day now, and I'll be able to get back to this.

In TunerCats, I seem to have the ability to take out the lean code for either. Please rest assured, I'm only looking at doing this as a troubleshooting step.

 

I've been updating the wrong thread... ALDL cable showed up yesterday...

I was just logging on to announce my new ALDL cable is finally here. Is there any data logger you like over any other?

I didn't mean i was going to run around all summer with the O2 shut off... Only as a troubleshooting step... I know I have to log a trip, so I took tomorrow off, and will be going for breakfast in the AM. It's about a 20 to 25 min drive, depending on the traffic. A couple starts/stops along the way, I won't pedal it at the stops so that you can see the rich condition at idle.

Shout out to RedDevilRiver.com for the ALDL cable. preliminary tests look much better than my old cable. (this one passes)

So now I'm going to go and try to read my existing ECM, set my tire size, and see about logging something in the yard here.

Again, thank you for all the suggestions and advise. I'm looking forward to finally having this thing running correctly.

 

then, this ...

Couldn't wait..

Seems that this cable is slower than what I remember from the previous cables, but it's working.

I have a quick EEHack file on my Google Drive if anyone once to take a look at comment.

I see the MAF code (there's next to no vac with this engine) and the O2 reading lean. I'd love anyone's input, the EEHack file can be found here:

https://drive.google.com/drive/folde...WK?usp=sharing

Thank you all.

 

and finally this. .

So, as a test, I disabled that Right O2 sensor. It is running smoother, still a bit rich, but I would expect that from Solomon on the first tune file anyway.

I've uploaded that EEHack file to the link as well. https://drive.google.com/drive/folde...WK?usp=sharing

SO, O2 checks out fine, wires all check out fine up to the connector to the ECM, so process of elimination, I have a spare ECM here that I can swap in, and program to see if the problem goes away or not I guess... Unless someone has a better suggestion.

Thanks again for any/all suggestions/recommendations.