Engine Monitoring Feedback: Lazy O2 Sensor?

Blckshdw

Original poster
Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
OK, as some of you remember, I had some concerns about my engine's behavior following a transmission and water pump replacement a couple months ago. I've been looking at Torque from time to time while on the road, as well as looking at other people's threads and screen shots when I noticed something today... My upstream O2 sensor, while it does oscillate (most of the time) it doesn't appear to be doing it anywhere near as quickly as I've seen it for others.

Managed to record half of my morning commute, wanted to see what others think about this. Here's a couple quick notes:

:32 Idling at a red light. O2 sensor movement not oscillating, but steps
1:00 leave from stop
1:12 Falls out of closed loop due to engine load (never seen this before)
1:19 Back into closed loop
2:00 Falls out of closed loop due to low temp for 12 seconds
2:17 Decent length of forward motion, stop and go traffic the rest of the way

Also, the knock counter usually pops up with some number at the beginning of my drives and it stays at that value until I got to my destination. But this time, continued to increase periodically. Should this be a concern?

 

xavierny25

Member
Mar 16, 2014
6,323
Staten Island, N.Y
I've seen a few different pics of members torque screenshots and never seen an o2 react in that fashion. I'd replace it and see where that gets you. It could just be a lazy o2.

At the moment I'm trying to figure out my own issue with stft, ltft and intake air temp.

I just got done cleaning and oiled up my green filter. I'm just waiting for it to dry to put it all back together. I also cleaned the maf sensor with some maf sensor spray cleaner. I'll take a run and record what it's doing now.
 

xavierny25

Member
Mar 16, 2014
6,323
Staten Island, N.Y
Video is a bit long but it covers about 10 block drive with stop and go for traffic light and a 7 minute run on the highway with a stop followed by another 7 minute run back home and the stop and go till I found a parking spot.
 

Matt

Member
Dec 2, 2011
4,019
I'd be changing that O2 sensor. It looks like it's getting really lazy to me.
 
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Blckshdw

Original poster
Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
Yeah, mine definitely isn't responding very quickly. Guess it's time to invest in an O2 sensor socket. :smile:
 
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Maverick6587

Member
Dec 16, 2018
730
Sterling Heights, Michigan

Blckshdw

Original poster
Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
That's the type I was looking at too, for the same reason. Did it come out easily, or did you have to run the engine to warm it up, or spray penetrating fluid to loosen the threads?
 

Maverick6587

Member
Dec 16, 2018
730
Sterling Heights, Michigan
That's the type I was looking at too, for the same reason. Did it come out easily, or did you have to run the engine to warm it up, or spray penetrating fluid to loosen the threads?
I tried with a cold engine and it seemed like I was going to snap it. I ran the engine for about 5 minutes and then it didn't come out too difficult at all. It was about like removing a lug nut that was torqued on a little too tight.

I couldn't get the thread chaser to screw into the threads at all, I tried for about 5 minutes. I got scared that I was going to ruin the threads so, I just put the new O2 sensor in without chasing the threads. It went in fine and then I just torqued it to spec.

EDIT: Here's the thread chaser I used if you want to be safe.
Lisle 12230 Oxygen Sensor Thread Chaser
 
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Sparky

Member
Dec 4, 2011
12,927
Having fought with one of these sensors years ago, I would highly recommend spraying it with pb blaster daily for 2-3 days before removal. Pb blaster and a few heat cycles over time works wonders. Going at it day of SUCKS. That sucker has been in there for how many years and heat cycles.
 

Blckshdw

Original poster
Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
I would highly recommend spraying it with pb blaster daily for 2-3 days before removal.

I was considering this, and wondering where my can was, since I haven't used it in a while. Thanks for the confirmation.
 

Blckshdw

Original poster
Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
Swapped out the O2 sensor and ran some errands. Torque shows the same behavior out of the replacement sensor, so that's not it. Anybody have any other ideas?
 
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whodwho

Member
Mar 7, 2019
41
CA
A couple observations I see is the O2 seems to be reacting but the STFT is not switching quickly so the O2 isn't. It also seems that it doesn't want to get over 190* even by the end of your 22 min video.

Edit: looking again the 2nd video the STFT is switching but that first one looked a bit odd
 
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mrrsm

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Member
Oct 22, 2015
7,642
Tampa Bay Area
The O2 Sensor may be providing the RESULTS of something that is happening well ahead of it with many other Sensors; All and Singly, working in weird combinations that can skew its (their)behavior. This Link can help us review all of the other 'Sensors in the Loop’ so to speak and perhaps kindle some interest elsewhere around the Engine as the real cause and origin of the Open Loop - Closed Loop Drop-Out Problem:

Trailblazer-Envoy Engine Sensor Locations and FAQWA (Frequently Asked Questions... WITH ANSWERS to Comments/Questions at the bottom of the Page::

https://www.greatautohelp.com/sensor-location/4200.html

Almost everyone following this Topic generally understands what an O2 Sensor is … But it never hurts to have MORE Information about their Designs/Functions/Foibles to add to and improve upon the chances of getting a Better Diagnostic Dial-In to figure out the present problem:

https://www.pakwheels.com/forums/t/oxygen-o2-sensors-diagnose-and-replace/37182

@MAY03LT delves into his suggested procedures for dealing with an O2 Sensor on the GMT-360 Platform Vehicles that simply refuses to be replaced...AND.... The Bonus is that he Follows Up with using his "GYMKO" Tech 2 to Diagnose the differences in perfromance between the Bad O2 and the New One:

 
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gmcman

Member
Dec 12, 2011
4,656
@Blckshdw what bluetooth dongle are you using? Looking at the video even the STFT seems to be locked in place. Does your TB run ok?

Were you able to record that video through the Torque app? If so very cool, will need to try that.
 

Blckshdw

Original poster
Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
@Blckshdw what bluetooth dongle are you using? Looking at the video even the STFT seems to be locked in place. Does your TB run ok?

Were you able to record that video through the Torque app? If so very cool, will need to try that.

I bought this one last year, replacement for the same model that I had been running for years prior.


The STFT swings a little bit, but because it stays fairly close to 0, I figured that was fine. For the most part the truck runs well. I've had this occasional "stumble" for a few years now, that I haven't been able to figure out. Usually while low speed coasting (coming to a stop, or stop and go traffic) I'll get that dirty throttle body-like hesitation like it's about to stall and then the engine will recover. Only twice in the last few years has it actually stalled though. My idle has gotten slightly rougher lately, but I know my passenger side motor mount has been split for about 2 years now. I have a replacement set, just haven't gotten around to swapping them yet.

It took me a while to find a screen recording app that I liked, that also worked on my Android HU, and didn't have annoying water marks. I settled on Mobizen Screen Recorder.

90617
 

gmcman

Member
Dec 12, 2011
4,656
@Blckshdw , thanks for the links....very helpful app!

I did a quick vid of mine, this was starting on a slight downgrade then a stop, STFT stabilizes a few sec after the stop.

I'd say your 02 sensor if that's the issue is long past lazy for sure...may need a de-fib.

Again, thanks for the info...very cool app.

 
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Blckshdw

Original poster
Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
Always glad to give a little back and help folks out. Glad you're liking the app so far. Think I tried 5 or 6 others before settling on this one.

Actually, I replaced my upstream O2 sensor last weekend, and get the same readings, so whatever is causing it, the sensor isn't at fault. Not really sure what else could be it. My PCMofNC tune got flashed back to stock when the stealership replaced my transmission in April, so I know that's not it. (Bad settings due to a tune)
 
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gmcman

Member
Dec 12, 2011
4,656
I'd be changing that O2 sensor. It looks like it's getting really lazy to me.

Yeah, I agree.

@xavierny25 how old are your spark plugs?

Also, your coolant took quite awhile to get over 190. When idling, was your A/C on?

Your LTFT while trending positive, your total fuel trim isn't extremely biased towards positive, however still a good push for more fuel. So I would look at your intake manifold bolts, check all 10. Also check your brake booster check valve.

@Blckshdw , what looks odd is it almost appears to lose communication but that's just saying the response is so slow. Have you verified the bluetooth adapter works on another vehicle? I would check just to be sure.

Surprised to see it goes into open loop with the temp at 195 deg, that's definitely weird.

Maybe check your PCM harness for any mis-aligned pins, not sure if the transmission ground or wire harness would cause any of these issues but you said it was removed.

Just something else to check, not sure if it would have any bearing on your issue, but the fan harness at the LH side of the radiator shroud...make sure it's properly seated and no wires are loose. I think it incorporates one of the 5V reference wires and may or may not cause other issues. The 02 sensor makes it's own voltage which should affect the STFT but still a box to check.
 
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xavierny25

Member
Mar 16, 2014
6,323
Staten Island, N.Y
@xavierny25 how old are your spark plugs?

Also, your coolant took quite awhile to get over 190. When idling, was your A/C on?

Your LTFT while trending positive, your total fuel trim isn't extremely biased towards positive, however still a good push for more fuel. So I would look at your intake manifold bolts, check all 10. Also check your brake booster check valve.

Spark plugs replaced 4-5 months ago.

Ive replaced 3 thermostats over the years and this is pretty much the hottest my coolant has ever run. Previous was a Stant that would never get me over 185. This acdelco gets up there to about 200 but always seems to settle between 190-195.

Honestly I've been lazy about looking into the intake bolts but might dive into that today.
 
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xavierny25

Member
Mar 16, 2014
6,323
Staten Island, N.Y
Have you ever changed the coolant temp sensor? If not, always good practice to change with the t-stat.

On the last thermostat I replaced I did swap out the temp sensor.

Took a video of a drive today I'm going to shorten it a bit and post it. I went at the intake bolts and there all torqued down on there good. I backed them out 1/4 " and torqued them and they landed just about the same.
 

Blckshdw

Original poster
Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
@Blckshdw , what looks odd is it almost appears to lose communication but that's just saying the response is so slow. Have you verified the bluetooth adapter works on another vehicle? I would check just to be sure.

Surprised to see it goes into open loop with the temp at 195 deg, that's definitely weird.

Maybe check your PCM harness for any mis-aligned pins, not sure if the transmission ground or wire harness would cause any of these issues but you said it was removed.

Just something else to check, not sure if it would have any bearing on your issue, but the fan harness at the LH side of the radiator shroud...make sure it's properly seated and no wires are loose. I think it incorporates one of the 5V reference wires and may or may not cause other issues. The 02 sensor makes it's own voltage which should affect the STFT but still a box to check.

I don't have a 2nd vehicle handy. I'll have to talk my sister into coming over, and driving me around for a bit so I can test the adapter in her car.

Came across a nice surprise when I opened the hood a lil while ago. I had coolant sprayed on the sides of the engine bay, as if it was getting onto the fan, and getting flung outwards. :eek:

90627

90628



At first I thought it might be the paper gasket from the replacement water pump, but the front of the engine, pulleys and belt are all clean. Also no drips on the garage floor. There's traces of coolant on the very top of the radiator... So I'm thinking maybe an issue with the upper radiator hose?

9062990630

I had never seen my fuel status drop out of closed look like that, until recently, so I'm assuming there's a correlation here. Checked the radiator, and it was still full, but the reservoir appears dry. I felt around the radiator end of the hose, didn't feel any splits or wet spots underneath. Going to adjust the clamp, rap a blue shop towel around the hose and fill neck, and go for a drive. Get the truck up to temp to open the t-stat and then see if that's where the leak is.
 

gmcman

Member
Dec 12, 2011
4,656
I wonder if the coolant is low/ has an air pocket?

Still showed 195 deg so surely a weird situation.
 

Blckshdw

Original poster
Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
Confirmed the leak location. Sprayed and wiped everything down to get it clean, then went for about a 30 minute cruise. Ran the AC for a change, for the most part stayed around 195, got into some congested stop and go traffic, and got up to 202. Driver's side of the upper tank has a hairline crack in the top of it, and was wet when I popped the hood after getting home. Wondering if it could be plastic welded and repaired. :undecided:

90631


Looked up some prices on replacements, and came across an upper tank piece sold separately? :confused: I didn't know this was a thing.

 

gmcman

Member
Dec 12, 2011
4,656
Looked up some prices on replacements, and came across an upper tank piece sold separately?

A popular repair for radiator shops but unless you want to mess with all those tabs, I would just replace the radiator. If the radiator is old then you remove the option of your current radiator loosing it's ability to transfer heat as efficiently as a new one.
 

Blckshdw

Original poster
Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
Definitely don't have the patience for all those tabs, would likely end up stabbing myself in the eye out of frustration. Too bad I don't know how to weld yet, or I'd buy a thicker radiator, fab up some mounts, and slap some e-fans in there.
 

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