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Oxygen sensors...

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Oxygen sensors...

Post  Remaggib on Sun Mar 31, 2013 3:30 pm

Trying to determine the problem of my sister in law's car, and I only have it for this week. Throwing engine codes (will get numbers later) and running rough, stinks when idling. Thinking Bank 1 Sensor 1. What should voltages be sensor 1 to sensor 2, in voltage, if that makes sense? 4 sensors total, both banks, sensors 1 and 2 on each. Will update more later, but just wanted to get those gears turning. Thanks!
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Re: Oxygen sensors...

Post  Simcik on Sun Mar 31, 2013 4:28 pm

Voltage should be between 0 and 1 volt on all sensors. If its running rough, its most likely your upstream sensors - they control fuel ratio.
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Re: Oxygen sensors...

Post  StalkerStang on Sun Mar 31, 2013 8:48 pm

Don't shotgun stuff.

Pull the codes first before buying anything or testing anything for that matter. If you have a lean or rich code, it could be the sensors working correctly and telling you so. Knowing O2 voltage is pointless for someone with basic tools. Need a scanner to make sense of that sort of data; more specifically the pattern the voltage creates.

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Re: Oxygen sensors...

Post  Remaggib on Sun Mar 31, 2013 10:23 pm

I have a cord that hooks up to OBDII and to my laptop and I have a program for it that reads a bunch of info. What I saw at one point was Bank 1 Sensor 1 had .150 volts, Bank 1 Sensor 2 had .750, Bank 2 Sensors 1 and 2 had .750 also, so that kind of caught my eye. Codes are P0174 P1131 P0171 P1151 on a 2001 Mazda Tribute. So a Bank 1 lean code is showing, I've been told it can be O2, EGR, or MAF gone bad but am leaning toward O2 mainly because there's a bad stench when idling even with the ass end out of the garage, and the chugging/surging that it does in drive. Just wanted to get anyone's input that may have a different route to try, but wasn't able to relay much info earlier as I was holding up half the family leaving for the Easter party today. So, O2? Or clean MAF and test (if even possible) EGR? Or just blow it up?
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Re: Oxygen sensors...

Post  StalkerStang on Mon Apr 01, 2013 1:37 pm

According to your codes Rem, you have a lean condition on both banks, with both O2 banks responding.

I would start with simple things first, check for vacuum leaks, clean the MAF, and maybe check the fuel filter or fuel pressure.

Just seems unlikely both O2's take a shit at the same time. Plus its lean on both banks.

I don't know how you are interpreting the O2 voltages, they are not constant voltage, they should be changing while the car is running. Its more the signal/wave they produce that shows issues.

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Re: Oxygen sensors...

Post  OLDFenderBender on Mon Apr 01, 2013 2:21 pm

I've had a friend's truck have a similar issue, it would idle just fine, but it couldn't get of to highway speeds (50ish mph), it was either a fuel rail or the fuel pump had gone bad (there was a loss of pressure at high speeds). Also when my father had a SVT Contour a while back, there was an issue with car idling (it'd keep stalling with out pressing the gas pedal). We ended up changing the fuel pump, MAF sensor, and a few other components (this was about 10 years ago though).

Like Stalker said check the fuel pressure and fuel filter first. As for that smell at idle, it might be coming from the headers or some where near there, may want to check for cracks or a broken seal.

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Re: Oxygen sensors...

Post  Remaggib on Mon Apr 01, 2013 5:54 pm

What's really weird is that the car ran fine before they took it in for an oil leak. Tires Plus fixed the oil leak (still don't know what the issue was, possibly a main seal) but then on the ride home the engine light came on, and it started chugging at stop lights and such. Warmer weather seems to favor the car more, and it doesn't act up as much. Get below 35 degrees and it starts getting real bad. Guess I'll check the MAF and try to clean it, and go from there.

As for how I'm getting the readings, I have a program on my laptop that reads all sorts of data from the car's computer. The voltages vary, but because the program reads so much it's only able to refresh everything about once every 1.5 seconds or so. But the voltages do vary, and what I'm seeing is what the ECU is seeing. Only the ECU makes better sense of it Mad
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Re: Oxygen sensors...

Post  Sorta05 on Mon Apr 01, 2013 10:27 pm

Try unplugging the MAF. If the car runs better that's your problem. This worked on a friends 5 series and WRX.
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Re: Oxygen sensors...

Post  Remaggib on Tue Apr 02, 2013 7:04 pm

Went to Auto Zone, printed off all 4 trouble codes. The similarity between all 4, MAF. So, Got a can of cleaner (have to order new part) and cleaned it, started out rough then after gassing it and going down the road it didn't do it again. But the engine light came back on (had cleared it Sunday) for system too lean on bank 1 and bank 2. But it runs fine, and to have a clogged fuel filter that throws a code I can only imagine how bad it'd have to be considering my father in law's truck had ZERO movement through it when trying to blow through it, and it never threw a code. But that was a Chevy and this is a Ford (wannabe) Mazda. So going to take it out tonight and see if it acts up. If it does not, I may try to get the owner to buy the MAF and go that route. But if it does it I will unplug the MAF, that's a great idea, thank you! Gotta love cars....
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Re: Oxygen sensors...

Post  Remaggib on Tue Apr 02, 2013 10:22 pm

It did in fact act up again, unplugging the MAF just pissed it off more. Now it has 8 engine codes. 2 for lean condition (both banks), a high input from AIT sensor, and cylinder misfires on 1,2,3,5, and 6. Maybe MAF isn't the problem?

To clarify in case I haven't, no loss of power when you hit the gas, and when moving it seems fine. Just when you stop the idle is... Surge-y. If it had no exhaust it would sound like a seriously modified high power race car engine. Any ideas? I only have it till Saturday. Without throwing parts at it I'm kind of stumped.
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Re: Oxygen sensors...

Post  Simcik on Tue Apr 02, 2013 11:01 pm

Umm, what is it you're working on? I guess it seemed to be the case this time, but alot of Mopars don't use MAFs, so you would have to go another route. Anyway, guess at this point it's just a curiousity.

And, if I remember correctly:

The B1S1 .15V reading indicates a very lean condition.
The B1S2 .75V reading indicates the cat is not functioning fully.
The B2S1 .75V reading indicates a moderately rich condition.
The B2S2 .75V reading indicates the cat is not functioning fully.

Like I said, I think that's the case. It should be that 0 is lean, 1 is rich, .5 is ideal, .6 or .4 should trigger the PCM to adjust fuel accordingly.

Some cars may measure the difference between S1 and S2, so perhaps their you're looking for 0, not .5V???

AND, most importantly, remember that OBDII codes are CLUES - not a diagnosis.
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Re: Oxygen sensors...

Post  Sorta05 on Wed Apr 03, 2013 12:18 am

When you go wot the car goes into open loop mode. Meaning it ignores all inputs from the O2 sensors. That's cause they are narrow band and can not accurately determine the a/f ratio needed for wot operation. But if the car is only have problems at idle or extremely light engine loads I would check out the EGR valve and look for vacuum leaks. Some EGR's are diafram/vacuum operated and can easily be checked for function. Others are electric and not so easy. If none of that is it and your still having problems it could be the primary o2's, but usually they only cause bad gas mileage.
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Re: Oxygen sensors...

Post  StalkerStang on Wed Apr 03, 2013 1:58 am

I agree with Sorta...

Start simple, vacuum leaks, EGR, take a look at some plugs, fuel filter. Most of these things cost nothing.... I still don't see how you guys can interpret O2 sensor voltage without seeing the wave they produce and real time data.

BTW no sensor should be at a constant 0 or at constant max voltage while the engine is running, that indicates an open or short in the circuit.

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Re: Oxygen sensors...

Post  Remaggib on Wed Apr 03, 2013 8:30 am

EGR seems to be working, it's a vacuum and I was able to close it by pulling air through it with my mouth. Maybe it's the purge valve? Going to check the vacuum lines today after work. It's just odd that right after it goes into a shop this happens, but could be coincidence. I really want to get this damned thing fixed so I can get around to putting the battery in my motorcycle and going for a ride, supposed to be nice tomorrow.
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Re: Oxygen sensors...

Post  Simcik on Wed Apr 03, 2013 8:39 am

StalkerStang wrote:I agree with Sorta...

Start simple, vacuum leaks, EGR, take a look at some plugs, fuel filter. Most of these things cost nothing.... I still don't see how you guys can interpret O2 sensor voltage without seeing the wave they produce and real time data.

BTW no sensor should be at a constant 0 or at constant max voltage while the engine is running, that indicates an open or short in the circuit.

The "wave" they produce can be measured with a good multimeter.

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Re: Oxygen sensors...

Post  Simcik on Wed Apr 03, 2013 8:44 am



Aww, the good ol' 3.8L injector tick...
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Re: Oxygen sensors...

Post  TuxTshirt on Wed Apr 03, 2013 10:47 am

The 4 original codes are the ones you should focus on. All 4 have something in common: lean condition. Either you've got too much unmetered air going into the combustion chambers or not enough fuel. Stuck open EGR doesn't give you too much oxygen as there's not much oxygen in spent exhaust gases, it will give you poor performance and, sometimes, stalling however. It's unlikely you have an exhaust leak that's causing an erroneous lean reading on both banks as well.

If this condition actually did coincide with service, what service was done? Did they touch something that could trigger a manifold leak? Did they remove the manifold for any reason? Did they cut an EGR tube seal? Do you hear anything that sounds like a vacuum leak? Do you have a vacuum gauge? Do you have a fuel pressure gauge? If you have a scan tool that can read 02 readings, can you also read downstream values? Can you read long-term adaptive fuel trim values? All of these are clues. What's the year, make, model, engine?

Last question:
If this started after a service, was the shop that serviced the vehicle contacted?


Last edited by TuxTshirt on Wed Apr 03, 2013 10:57 am; edited 1 time in total

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Re: Oxygen sensors...

Post  TuxTshirt on Wed Apr 03, 2013 10:51 am

StalkerStang wrote:According to your codes Rem, you have a lean condition on both banks, with both O2 banks responding.

I would start with simple things first, check for vacuum leaks, clean the MAF, and maybe check the fuel filter or fuel pressure.

Just seems unlikely both O2's take a shit at the same time. Plus its lean on both banks.

I don't know how you are interpreting the O2 voltages, they are not constant voltage, they should be changing while the car is running. Its more the signal/wave they produce that shows issues.

If there is indeed a lean condition, which it sounds like, the O2 sensors may not, and most likely will not produce a wave as they're unable to due to the excess oxygen.

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Re: Oxygen sensors...

Post  Simcik on Wed Apr 03, 2013 12:13 pm

Oh, Jeez, Tux went all "long term adaptive fuel trim" on him...

Haha - it just sounded funny to me. It is helpful though to know that stuff though. Been there, done that a time or two...
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Re: Oxygen sensors...

Post  Avanti 63r1025 on Wed Apr 03, 2013 3:37 pm

Type of vehicle was in Rem's first reply post Wink 2001. Mazda (fake Ford). Tribute (fake Escape). Complaining about 2 banks, so it's a V6 model.
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Re: Oxygen sensors...

Post  TuxTshirt on Wed Apr 03, 2013 4:14 pm

Avanti 63r1025 wrote:Type of vehicle was in Rem's first reply post Wink 2001. Mazda (fake Ford). Tribute (fake Escape). Complaining about 2 banks, so it's a V6 model.

Apparently I can't read.

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Re: Oxygen sensors...

Post  Remaggib on Wed Apr 03, 2013 5:39 pm

There was an oil leak, I thought it was coming from inside the timing cover so they took it in. This was on the passenger side of the engine, EGR and all that is more on driver's side. I can't hear a vacuum leak, don't have a vacuum gauge, I think the program I use is OBD Wiz or something, pretty nifty. I can probably get long term fuel air oxygen explosion something readings, will try to do that tonight. I believe the shop said that they can't do anything about it because they really don't have any proof it happened there. It's Tires Plus, the same place that told my father in law that he couldn't have his tires rotated and balanced because they would need to add 8 pounds of wheel weights to the rear tires to balance them.
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Re: Oxygen sensors...

Post  Remaggib on Wed Apr 03, 2013 5:47 pm

Simcik wrote:
StalkerStang wrote:I agree with Sorta...

Start simple, vacuum leaks, EGR, take a look at some plugs, fuel filter. Most of these things cost nothing.... I still don't see how you guys can interpret O2 sensor voltage without seeing the wave they produce and real time data.

BTW no sensor should be at a constant 0 or at constant max voltage while the engine is running, that indicates an open or short in the circuit.

The "wave" they produce can be measured with a good multimeter.


Is the multimeter in this video considered a "good" one? Because it's the exact same as what I have in my car for work. affraid
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Re: Oxygen sensors...

Post  Simcik on Wed Apr 03, 2013 10:04 pm

No clue, but is that one can do it, I'm sure other can. You just need one that has a good response time to try to watch it real time.
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Re: Oxygen sensors...

Post  Remaggib on Wed Apr 03, 2013 10:11 pm

STFT was at idle around 23 to 25, LTFT the same. Driving, the STFT would dip to -3 or so and the LTFT would average around 10 to 15. No idea what any of this really means, I did read up on it but may only have a general idea. Also heard a vacuum leak when I pulled the top cover off the engine, traced it to the EGR valve where it goes into the engine. With engine surging at idle, I sprayed some MAF cleaner around it and the idle picked up. Pulled it all apart, cleaned the tube going into the engine, cleaned the rubber seal and reversed it, reassembled and can't hear vacuum leak. As for surging it didn't seem to do it as much, but the engine light came on within minutes of starting up and idling in the parking lot. That's when I grabbed the laptop and took her for a spin around the block, getting the fuel trim numbers.

Too bad I had to nail the wrong pedal when I saw that family of deer crossing the road, could have solved this problem quite quickly. No
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Re: Oxygen sensors...

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