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General Wideband O2 fail with lamba stuck at 1.00?

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Kruthers

Probationary Member
17
1
May 8, 2019
Harrisburg, Pennsylvania
I've been trying to diagnose a new problem - car stumbles/hesitates horribly under high boost. Zeitronix ZT2 wideband O2 reads a lamba of 1.00 at all times, AFR stays at 14.8 during accelaration or lift, only sometimes flickering to 14.7.

So the question... is this a likely symptom of sensor failure? Seems like a failed sensor would get stuck at any other value than that, but I don't know. Any suggestions?
 
Take it out. Soak a rag into fuel an wrap it around the o2 sensor and see if the gauge will change its reading. If it does not then I would start with changing out the sensor. It's not often but it does happen that o2 sensors get stuck.
 
How are you getting the AFR from the sensor, through viewing the gauge or through datalogging? If it's from datalogging, what logger are you using? Are you logging through a 0-1V sensor input to the ECU?

Something to note, a wideband delivers info by varying it's current output not voltage. When there is positive current flow afr is getting leaner, when there is negative current flow it's getting richer and at no current flow the sensor is declaring a stoich mix.
 
How are you getting the AFR from the sensor, through viewing the gauge or through datalogging? If it's from datalogging, what logger are you using? Are you logging through a 0-1V sensor input to the ECU?

Something to note, a wideband delivers info by varying it's current output not voltage. When there is positive current flow afr is getting leaner, when there is negative current flow it's getting richer and at no current flow the sensor is declaring a stoich mix.

I was reading it from the digital display, didn't get datalogging to work yet. Will hopefully get the zeitronix datalogger working tomorrow and see if it reports the same.

Very interesting about the pos/neg current. That suggests it could be completely dead and reporting what I see.
 
Take it out. Soak a rag into fuel an wrap it around the o2 sensor and see if the gauge will change its reading. If it does not then I would start with changing out the sensor. It's not often but it does happen that o2 sensors get stuck.

Yeah between you and delta448 it appears that's what I gotta do. It's a pain though so just wanted to check before going through with it. Thx.
 
I've been trying to diagnose a new problem - car stumbles/hesitates horribly under high boost. Zeitronix ZT2 wideband O2 reads a lamba of 1.00 at all times, AFR stays at 14.8 during accelaration or lift, only sometimes flickering to 14.7.

So the question... is this a likely symptom of sensor failure? Seems like a failed sensor would get stuck at any other value than that, but I don't know. Any suggestions?
Maybe this doesn't solve your issue but just sharing my experience. I had a similar issue with a PLX M-300TE. Sometimes the gauge display got frozen and required to restart the unit. In my case, the issue was a poor connection between the sensor harness and the module. The sensor itself was fine.
 
That suggests it could be completely dead and reporting what I see.

In my case, the issue was a poor connection between the sensor harness and the module. The sensor itself was fine.
This is what I was getting at. Also, soaking a rag in fuel and wrapping it up leaves a lot of room for misinterpretation. The sensor doesn't care how much fuel is there, it only wants to compare the relative oxygen concentration to atmospheric.
 
Well I might be barking up the wrong tree. It does look like the wideband O2 sensor is probably bad; it's bent and the cable insulation is ripped. I reseated all the connections (thx DSMPT for the suggestion) but no difference.

But it's not in place of one of the stock O2s. Yeah I'm just finding this out now... I didn't install it, or the zeitronix or tuning, it was all done by a shop a long time ago. Never realized they added a 3rd bung for the wideband.

This means the zeitronix is not doing simulated narrowband, so even if this is broken it should not affect how the car is running. Damn back to square one.
 
Now that we got that out of the way the hesitation is most likely ignition system related. Pull the plugs and inspect them. Make sure you are using correct plugs, check the gap, change them. Normally hesitation is misfires. Question is which cylinder and what is causing it. You need to know that your ignition system is in good shape and you need to know if you are not running too lean or rich. It Is possible to have a bad injector but that it is not very popular. Good luck and keep us posted.
 
Well it's not the plugs, I just replaced them (or the wires, I replaced those before posting). Though strangely the hesitation is different with the new plugs. Instead of random stumbling it's very consistent now, like machine gun fire. Very weird.

It only happens during high boost, like 14-15psi and above. High rpms are fine as long as boost is low.
 
What brand of the plugs and wires used? About 15 years ago I bought my first dsm. It was 97 gsx in red with badge leather. I miss that car. Anyways it had a very bad misfire/hasitation from like 3k rpm and up. I remember even back then reading on tuners about useing correct plugs. I drove like that for few months as I was a high school student and had no idea what I was doing. Once I gained some courage and pulled the plugs and I found Bosch platinum plugs. As soon as I changed them to ngk my hasitation went awey. I never even checked the gap or change the wires. Moral of the story doable check which plugs you installed. By any chance can you check if you set any codes? Maybe pcm picked something up, maybe we can identify a cylinder. I don't know if 2g have mode6 but If it does then you need to look and see if it has results for misfires. Test number somewhere in the 50s. I can't believe no one has stormed in and said check boost leaks. I think the forum is loosing its touch. Haha.

After simple checks I would turn the boost down if possible to like 10psi and get my wideband working properly and monitor afr during boost. Maybe just maybe it leans out or floods out. Depending what you find will pull you in differant directions. Also I would monitor load and mass air flow reading. During wot operation your load should come up to over 90%. At least. If it does not you mass is not working right. Your fuel pressure should rise with boost. Install fuel pressure gauge and tape it to the windshield and go wot and see if the pressure rises with boost. Also something to check, maybe 2g does not have it I don't remember anymore, check the ptu by moving the harness around and or taping it screw driver or even apply heat to it. My connecter to ptu is terrible and if you were to move it around with running car the car wants to misfire and run rough. I still think it's ignition related. Normally the ignition system starts to act up and develop misfires. Rarely it's some thing else.
 
Man lots of information, thanks guys. I may not post back for a while, life getting in the way for a bit. But you guys are leaning heavily to the ignition side so I'll keep looking into that.

@Brembo: I had cheapo autozone plugs and wires for a while without problems, and now that this has come up I've replaced them with NGK, hoping that was it. So no luck there. I also checked the gaps before installing them, they were more like .030 or .031 which is the top end of the spec, but I can't imagine new plugs would cause such severe symptoms when crappy ones worked before.

The car sat around a lot for the past few years and it's been really wet here in the east, so maybe it's just taken a toll on the ignition system?

Anyway, I'll try as many of your suggestions as I'm able to and report back in a while. Thx again...
 
Well it's been a while but I finally got a new wideband O2 installed and did some of the tests you guys suggested. The 2ndary coil resistance was right on the money and the primary coil was around .9 ohms. That's slightly off but my ancient fluke meter is really inaccurate down that low so it's plausible that the coil resistance is fine.

Hopefully the afr graphs will be more useful. This first run I did 2nd gear 60% throttle then 3rd gear full throttle, and needless to say it is still stuttering/hesitating. To be honest I don't know what afr should look like, but this graph just seems wrong to me. Have a 2nd run that I'll post next...
 

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Here's the 2nd run, i think it was 3rd gear then 4th gear both full throttle. Again the afr seems weird, it sorta leans out and wavers around? Is this what weak fuel pressure looks like?
 

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Going from the second graph.

Someone correct me if I am wrong but the first cursor is perfect. You are 13 pounds of boost and 11 afr. Plus egts are cool.

The second one, your in vacuum. So Afrs are repflacting that. I would have to say maybe play with injector squirt thing in ecmlink to squirt more fuel when you stump it. Also it seems like the afr are going down as the rpm grow. So work on your target afr and adjust accordingly so that wideband matches the target afr. To me it looks like you need to work on calibrating your target Afrs to actual.

Also what program is that snapshot from? Looks interesting.
 
Ok makes sense, been hesitant to mess w/ the tuning b/c I don't wanna blow it up, heh, but what the heck.

But if the tuning hasn't changed, is it plausible that a failing fuel pump could do this? Or would that look totally different. I should probalby take your advice and install a pressure gauge but haven't looked into what that entails yet...
 
Ok makes sense, been hesitant to mess w/ the tuning b/c I don't wanna blow it up, heh, but what the heck.

But if the tuning hasn't changed, is it plausible that a failing fuel pump could do this? Or would that look totally different. I should probalby take your advice and install a pressure gauge but haven't looked into what that entails yet...

Everything is possible. The only way to find out is go actually monitor fuel pressure and see if it is where it has to be. Also it is possible that the scan tool that captures data and the sensors like wideband and map might have slight delay. Meaning that the logger is to slow to capture fast enough. If that makes any sense.

I keep going back and analyzing the data. The second cursor say 99 tps. 1.6 boost and afr in 16. I would check fuel pressure and actually the injector tip in squirt. It would be nice to have logable fuel pressure reading so that you can analyze data better. Also battery voltage plays a key role how much pressure the pump will give out. Make sure it does not dip.
 
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But I still would like to know what software is that snap shot from? Also if it Is possible move the cursor on run 2 to the end of the wide open throttle. If you study the graph it looks like when you stab it it goes lean a bit then The afr graph goes low and then start to rise back up even though you still wot and boost is climbing. Interesting graph. Now that I see that( must of look at it like 10 times) it does look like it is leaning out but interesting fact is that egts are still the same as before, or very small rise, so I would imagine if the car is running lean then egt would react accordingly. Now I would really like to see fuel pressure readings. It's possible that regulator is not doing what it has to do. Either case you need to start running some tests.
 
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Yeah not sure why I didn't put more cursors on the 2nd run but here's another snap with a few more. These graphs are from the zeitronix datalogger.

As for the egt not shooting up, maybe it's because the afr heads towards lean but never actually gets fully lean during wot? In any case, I'm definitely suspicious the problem is fuel pressure or something related at this point.

Anyway, thx for all your suggestions, I'm really hoping to do some more testing this week...
 

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@Brembo and delta448 - Been a while but I did finally take care of this problem. Your intuition was right from the start: was the coils.

But before that I realized I had bad gas or water in the gas. Adding isoheet and running through a few tanks made things BETTER, but not solved. It did make the AFR graphs look good though. That left pretty much only ignition so I bought and installed some coils, and bam, that fixed it. Anyway, thx for all your input, was very helpful.

Here's a final graph to show a pull of about 8 seconds in 3rd gear. It's no beast but at least nice and strong again.

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