Advice for stripped threads upstream oxygen sensor exhaust manifold

[Clare Snyder]

If it was P0133 it means slow response - definitely a bad sensoe

[Clare Snyder]

Don't hurt your fingers. It worked.

[Arlen Holder]

I think that's what it was, but what only matters now is what comes back!

BTW, I just bought oxygen sensors for three different vehicles, where I

*hate* throwing parts at a problem. I just hate it.

But it turns out to be difficult to *test* oxygen sensors faithfully.

Sure, you can heat them up and look for a voltage, but after trying that, I gave up because a "really bad" oxygen sensor has its own code, but a "slightly bad" oxygen sensor seems to, in my humble experience on two different vehicles, cause one of two different related codes.

That is, in my experience, a. A slightly bad lambda sensor can cause a CAT register to never set b. A alightly bad lambda sensor can cause a "slow response" code

Given that the heat:voltage test of an oxygen sensor isn't really all that accurate for those two things, and given that oxygen sensors are not only relatively cheap but also known to not last more than about 100K miles, I decided on all three vehicles to just "throw the part" at the vehicle.

In the case of the neighbor's CAT register that wouldn't set, it worked.

The neighbor's kid's Mitsubishi is in testing.

I'm still working on the bimmer (having just this week replaced the two front Bosch upstrem lambda sensors).

What's amazing, to me, is that I've never replaced an oxygen sensor before, in my entire life, but I never worked on such old cars either (two decades old each of them).

Having zero prior experience with oxygen sensors, I think sometimes, "throwing parts" at the problem might be OK in the case of emissions codes because: a. Oxygen sensors are not permanent parts anyway, and, b. You have to get past smog (where a ticket is far more expensive), and, c. You can't really test them accurately (from my experiments anyway).

[Arlen Holder]

:)

I got some brand new stitches in my forearm last week, but it was due to a carbon dioxide, explosion and not from working on cars!

[Clare Snyder]

With a proper OBD2 tester you can see the voltage fluctuation while the engine is running. I can tell you in less than 15 minutes if the sensor is good or bad - while it is in the car (front sensor)

[Arlen Holder]

I have live data, and freeze frame on my OBDII tester, but I don't know what to look for (and yes, I saw that video on what to look for).

It didn't sink in mentally. I'm not sure why. I think I don't have the background to glean the details yet.

Anyway, as I said, all three vehicles have new oxygen sensors, and one already passed smog - the other two need the registers to be set first.

[Scott Dorsey]

You don't test them on the bench. You use the scanner. You set the scanner to give you a display of the oxygen sensor signal (and it will show the nominal level, but if it's so bad it's setting codes you'll likely see the pointer slammed to one side or another). So now you know what the computer is doing.

You also know what the engine is doing. The exhaust smells rich or lean. You can put your hand over the intake... if it runs better, the engine is too lean.

When you know what the engine is doing and you know what the computer is doing, you know all you need to know about the oxygen sensor. If the computer thinks it's too rich but it's really too lean, it's likely the sensor, but if the computer thinks it's too lean but can't enrichen it out far enough, it's likely not.

Timing and ignition problems will produce poor combustion which will show up as oxygen sensor errors... but you can see THOSE because the computer gives you ignition timing information.

The scanner will tell you all of the inputs and all of the outputs.

Ignore the damn codes. The codes let you know that something is out of range but it doesn't tell you anything else. Look at the plots. If you just spend your time staring at the codes you won't understand what is going on inside the box.

They do fail, but the vast majority of 'oxygen sensor' error codes have absolutely nothing to do with the oxygen sensor itself. They are faithfully recording that the exhaust is way wrong.

--scott

[Xeno]

It always amazes me the dependence people place on those codes without really understanding the *system* that is generating the codes and, in most cases, the *limitations* of those systems.

[Arlen Holder]

I agree with both you and Scott that *most people* (not me, but most people), when they see a sensor code, they replace the sensor.

It could be a temperature sensor for heaven's sake, and they replace the sensor.

As I told Scott, I'm an EE so I know how to test a sensor, but in the case of oxygen sensors, I've had five years' experience with the toyota and bimmer where a bad sensor will make the FTP not set the related monitors for hundreds of miles. IN the case of the toyota, it took about 400 miles, and it took more than a thousand in the case of the bimmer.

In *both* cases, I took it to the smog referee and passed with flying colors, even with the registers unset (since that's what the BAR smog referee did in years past). They don't do that anymore, so you're stuck now.

I know the FTP inside and out, and spoke to the BAR engineers who know it even better than I do. I went over all the dozen conditions that an engine must be in order for a monitor to be set.

Remember, in both cases, the bar smog referee PASSED the vehicle.

The problem is much more sinister than you seem to have experience with. But I do agree with you that *most people* just throw parts at a problem.

What I find hilarious is what happens AFTER people throw parts at a problem. Let's take the two corner cases, assuming, for example, that a problem can have FIVE (for argument's sake) caususes:

1. If they guess right on the first pass, they claim that they are an utter genius, and after that, for the rest of their lives, anyone who has that same problem, they swear the answer is that first solution.
2. If they guess wrong, and have to replace all five parts, they swear that the first four parts were bad, until they finally get to the right part.

Anyway, the main point here is that we all agree that throwing parts at a problem is a crazy way to "fix things" but you have to admit a lot of car problems are fixed that way.

I find the funniest "throwing parts" at a problem to be "brake warp". I'm sure the intelligent ones here know that street rotors just don't warp. So I will assume you know that. (Nobody ever measures warp - but it's easy to measure warp which you do measure for a head, for example.)

So what do the morons do when they get a brake-related vibration at speed? They throw rotors (& sometimes pads & even bigger calipers) at it.

Guess what? That solves the warp! Instantly!

They *think* they're an utter genius. They *think* they proved they had rotor warp.

Every brake vibration for the rest of their lives, is due to "warp". Hehhehheh ....

Q: Why does this work? A: Because the *short term* solution is *different* than the long-term one!

While brake-related judder can be caused by many things (look up the Tire Rack vibration flow chart as just one example), let's assume that judder was due to uneven pad deposition.

You can't measure that stuff (not with home equipment you can't). So the rotors measure fine (not that anyone who thinks they warp measures anything).

What happened in the case of "warp", is that there was uneven pad deposition (let's say for this case), and so, replacing (or machining) the rotors "solved" the problem but - get this - the warp comes back.

The guy who *thinks* the rotors warped is dumbfounded.

The short term solution solved the "warp", but the long term solution didn't. Q: What's the short term solution? A: Change your rotors (or machine them or rebed them).

Q: What's the long term solution? A: Change your braking habits.

My point is that, while I'm not a mechanic, and while I only have the experience of the cars that I own or that friends/neighbors own, I generally troubleshoot a problem to the UNDERSTANDING of teh cause of the problem.

In the case of oxygen sensors, I know, from my experience with two old vehicles, that an o2 sensor can be just bad enough to not set codes but to take between 400 and 1000 miles to set all the registers - even as the emissions are perfect.

If you can diagnose *that*, you'd be my hero! Likewise, if you can suggest a working $100 smoke machine, I'd love you!

[Arlen Holder]

You seem to have skills that I don't have since you can "feel" and "hear" things that I can't.

I do have live data and freeze frame though, but I'm not sure what to look for.

You seem to have sensitive powers of smelling that I don't have.

For example, it has been four or five years running now that the bimmer wouldn't set a register after clearing the codes (two different smog cycles) where, finally, after many hundreds of miles, the registers all finally will set.

And trust me, I know the FTP (federal test procedure) drive cycle, and specifically the BMW drive cycle just as well as you do. I've been on the phone with CARB for an hour, talking with the engineers, asking why a register wouldn't set.

I've been to the smog referee multiple times (always I pass).

No funny smells though. So you must have a very sensitive nose!

The first time I took it to the state smog referee who passed it even with the registers unset - and they literally took almost an hour - two people besides - to smog it. They climbed all over that car, looking for smoke, looking at the engine - looking up stuff in their Mitchells to see if it was modded - looking underneath, etc.

But now you can no longer effectively use the smog referee anymore.

No smells though. So your powers of smell are far greater than mine ever will be.

Remember, the sensor is working as the code is NOT an oxygen sensor code. There is no code on the bimmer. The register just won't set.

Again, you have powers of sense that I just will never have.

Anyway, lean is so easy to know about that it's not funny.

If the bimmer is running lean (and they all do, if you own a bimmer, you'll know why I can confidently say that), then you get a lean condition code.

The bimmer is filled with them.

The way I've learned to diagnose a lean condition is a good smoke machine. At least on a bimmer it is.

The CCV hoses, for example, are deep in the bowels of the engine. The secondary air tubes, for example, are way hidden near the top.

I made my own smoke machine, but it sucks.

Maybe. I think you know far more than I do. The only reliable data I would have is freeze frame and live data. On the Bimmer, I have INPA/EDIABAS on a PC (and DIS, Progman, etc.) so that tells me a lot.

But you have to know exactly what to look for. I don't.

I don't understand.

Timing, nowadays, isn't usually an issue.

You have to realize that I "think" that an "almost good almost bad" sensor is hard to diagnose. It won't set a sensor code. It will just prevent the related register from being set.

You have to understand that I'm an electrical engineer. I'm not your typical person.

You may think I'm the typical person. But I'm not. (Being an EE doesn't make me automatically a car mechanic though.)

The typical person, both you and I agree, sees a code "related to X", so they replace the sensor X.

Me? I test things.

If the sensor related to X has a code for X, then that just tells me something is wrong with: a. the power to sensor x b. the data inputs to sensor x c. the data outputs of sensor x

The problem you have to realize that the bimmer and toyota had, which the mitsubishi did not have, is that there were zero codes. The only problem was the cat-related register wouldn't set.

After speaking to CARB on the phone, who gave me all the reasons that could happen, we agreed, together, that the only thing that made sense was that the sensor was good enough not to set a code but just bad enough not to allow the cat-related readiness monitor to set.

On the Mitsubishi, it was different as it's a "new" used car so, since I didn't know the history of the sensor, I decided to replace it anyway since it could be as old as 175K miles for all I knew.

Yup. A slightly bad sensor can be nursed for five years & pass smog. (Ask me how I know that.)

It seems that you may not have had the experience I have with a sensor that is good enough to pass smog wonderfully, even by the BAR referee, but which is bad enough not to allow a cat-related register to set.

If you can diagnose that, from the live data and freeze frame data, I'd love to know how because that would be an art unto itself.

[Scott Dorsey]

Well, THERE is your problem. Look at what is going on with a correctly running engine.

It is a closed loop system. Data comes in from the lambda sensor, and once the machine is warmed-up and the system is running closed-loop, the oxygen concentration is used by the computer to set the mixture control.

You can watch it on the scanner... watch the sensor value when you open and close the throttle by hand, watch it when you squirt a little WD-40 in there. The output of the lambda sensor goes into a second order function that is nonlinear but time-invariant and what comes out is the error for the mixture. The mixture is adjusted in realtime based on that error value.

If you do not understand that this is a simple single-loop feeback system, we have a problem.

All that is nice, but who cares? Get the engine running well. When the engine runs well, you won't have to worry about smog testing. The key is to get the engine running well.

The bit gets set when a certain amount of time has taken place without particular parameters being out of range. If the bit isn't being set, something is going out of the nominal range. Looking at the values in the scanner will tell you what the inputs and outputs are, and if you have the BMW scanner you can see a lot of the intermediate calculations going on as well.

Stop wasting your time worrying about the bits not being set and worry about why the engine isn't running as well as it could be.

[irrelevant junk removed about diagnosing vacuum leaks]

That tells you EVERYTHING you need to know about what is going on with the computer. You get to see all the inputs and all the outputs, and you should have a pretty good notion of what the computer algorithm is if you have read the manuals.

NOW you need to learn to know what is going on with the engine, using your basic senses. When what is going on with the engine is at variance with what the computer sees, you have found the problem.

It's clear that you don't. It's a feedback loop. Do you remember control theory in school? The computer sees the input, it uses it to adjust the output. If the input is wrong, the output will be wrong in the opposite direction.

Ignition timing is OFTEN an issue. Valve timing isn't so often an issue, but you get a free valve timing test when you're checking the ignition timing anyway.

The computer controls the ignition timing, and it does so based on a number of inputs most notably the ping sensor. The computer will advance and retard the timing, and you can see it happening on the scanner display. It does not always do so properly.

In fact on some modern engines (like BMWs with VANOS), the computer has control over the valve timing and that might be based on feedback or it might just be a lookup table where RPM goes into the function and VANOS servo position comes out. Again, the scanner will let you watch it happening, the manual will describe how it's supposed to happen, and your brain can correlate the two.

This is because you're fixated on the codes. Stop worrying about the codes, stop worrying about the register bits, start worrying about how well the engine is running.

Then start acting like an engineer and stop acting like a board swapper.

Of COURSE you can diagnose that from the realtime scanner data. That's what the scanner is FOR. Stop worrying about the stupid codes, stop worrying about errors and register bits, start thinking about what it takes for the mixture to be correct and how far off the mixture is likely to be.

If the oxygen sensor output is in the normal range, but the injector duty cycles are all way out of the normal range, you have a mixture problem. Because the computer is working hard to move the sensor values into that normal range.

It won't set any codes, it won't produce any errors, but the car won't run right. Maybe you have a leak, maybe you have a plugged injector, maybe you have low fuel rail pressure. The computer lets you see that there is a problem, THEN you can start measuring things to see where it is.

Because the system is closed-loop, the computer will compensate for problems in the system... until it no longer can and THEN once it get catastrophically bad and something is totally out range, THEN it will set an error.

--scott

[trader_4]

It may not be that crazy if you're paying $120 an hour for diagnosis. It could be totally logical to replace two $30 parts, instead of spending an hour figuring out which one it is. If you're doing it yourself and the labor is free, then it changes the equation.

[Clare Snyder]

I'm going to call BS on this. Brake warpage is RARE - but certainly not impossible or unheard of.

Pad deposit issues are the MAJOR cause of brake shake across north america, followed by rotor corrosion (often related to pad deposits, but not always) - but heat related warpage or corrosion related parallelism problems are NOT uncommon.

Here in the rust belt, the corrosion issues are more common.

I have measured warpage in excess of .050" - on vehicles with NO brake pulsation complaints as long as the caliper slides/pins are free floating - but USUALLY when you have warpage it is BECAUSE the caliper is not floating properly and the rotor has become severely overheated (and then often differentially cooled - like hitting a water puddle) I've seen a few real TACO rotors. Not many over 50 years - but enough to make me say categorically that claims that rotors NEVER warp are WRONG.

Or the pad materials. Toyota had a situation years back where they changed the composition of their semi metalic pads from brass filings to iron - and all of a sudden they were replacing rotors by the pallet load.

Going back to the previous (brass) pads solved the problem.

On my '90 Aerostar with the OEM spec semi metalic pads, the rotors were always scrap LONG before the pads were worn out. I switched to a performance carbon metallic pad, and for the first time I could lock up the front brakes at ANY speed - and the rotors outlasted 2 sets of pads - which lasted much longer than the previous OEM brakes.

And I AM a (retired) mechanic - with LOTS of experience (including teaching the trade and competition driving)

I've got a "stage effrcts" fog machine I've been meaning to adapt as a diagnostic smoke machine. Paid about $30 for it.

[Clare Snyder]

That's where training and experience come into play

Again - experience

Which register won't set?

The only sure cure for Bimmer problems is a Lexus - - - -

The codes tell you what the computer is SEEING - or NOT SEEING - this gives an experienced mechanic the information to know WHAT he is looking for - it doesn't tell you necessarily WHERE to look - - -

Doesn't make you an electrician, or an appliance repairman, either -

- -

It is a comination of a "black art" and a "science"

[Vic Smith]

I've had 2 cars that threw an O2 sensor code. A Chevy, and my daughter's Mitsu. In both cases new sensors - and nothing else - was the total fix.

[Arlen Holder]

I don't disagree with you Clare as anything is possible.

Rotor "warp" is the classic case though of: a. Most who "claim" disc warp don't actually measure anything. a. Their short-term solution makes them feel like they are a genius b. But the long-term solution is different if they truly warped. I've noticed that most people who "scream" their rotor's warped, are only screaming it because it continues to happen to them (fancy that), and that they never seem to *measure* anything. They just assume rotors warp (as in potato chip).

Agreed. That's why changing braking habits is critical, IMHO.

I'm in California. If you looked at those pictures of the transmission and underside of the chassis of a 20 year old vehicle, you'll see corrosion isn't much of an issue here luckily. But I grew up in the rust belt, so, yeah, corrosion is a bitch as it can change runout.

I won't argue. I read all the reports. I know what they say. I just don't have the EXPERIENCE you have.

But I don't want to hear anyone talk about warp who didn't measure the warp, which is easy to measure, since it's the same type of measurement you use for a head (AFAIK).

Yup. I've literally put my fingers through rocker panels on cars in the rust belt. Not in California though. The environment is so easy here that people's brains are warped from life being so easy. :)

Steel doesn't get all that soft until reaching VERY HIGH temperatures. I'm never gonna say they "can't" warp though (& I never did say that).

I was just using it as the classic case of throwing parts at the problem.

If someone has uneven pad deposition, then throwing rotors at the problem year after year after year after year after year, is NOT the long-term solution.

Never say never. I didn't mean to say or imply that they "can't" warp. Just that it's a classic case of throwing parts at the problem.

The people who say rotors warp all the time on them say it year after year after year after year. They even put LARGER rotors on the 4Runners (as you're well aware) thinking that they were warping. So they spend HUNDREDS of dollars on the wrong solution.

Not one of them measures the warp. They simply throw parts at the problem.

And they think they're geniuses because the short term solution always works. But then they come back and scream that the brakes suck because they "warped again".

C'mon Clare ... you *must* have seen these millions of threads where guys scream year after year that their rotors keep warping on them.

True that some say you can get "race pads" which will reputedly "screap" the uneven pad deposits off the rotors.

But you can just "rebed" the pads and it will do the same thing from my experiences with deposition-related brake-related vibration at speed.

We have a huge thread on brake friction materials and testing of them.

My summary, after umpteen hours of research, is that it's not likely any individual stands any chance of being able to compare two brake pads side by side in his hands.

All he can do is "trust" the marketing (which I don't trust - and yes - I was in marketing for a while) and trust that the cold/hot friction coefficients apply to his driving style, vehicle, and terrain (it's hilly here).

Me? I dispense with all the marketing bullshit. They can put a fleck of clay and another fleck of metal and call it anything they want at that point (which has been confirmed by my own personal phone conversations with the Axxis/PBR/MetalMasters (bimmer) & Centric (toyota) engineers).

IMHO, there is more marketing bullshit in brake pads and rotors than in politics (and you never will hear me speak of politics because I hate bullshit).

Everything is "performance". It's all marketing bullshit. The difference between "metalic" & "semimetalic" is marketing bullshit. Marketing can say anything they want (and they do). All they need to do is put a fleck into the mix & they're home free. (I get this information DIRECTLY from both Axxis & Centric engineers.)

Everything marketing says about street pads & rotors is, IMHO, bullshit. Almost nothing that most people say about pads & rotors is, IMHO, fact.

Luckily, it's trivial to measure rotors. They either meet the minimum spec, or they don't.

And they're cheap too, nowadays.

I'm not gonna even touch the words "performance" "carbon" & "metallic". Just not gonna.

In my experience with you over the years, on PRACTICAL stuff, you're almost always, if not always dead right.

On theoretical stuff (like brake pads) we differ but not materially. I think a lot of what is "said" about pads and rotors is bullshit. You seem to believe it.

That's fine. It's OK to not agree 100%, as I will always say I don't have the experience you have, and I never will have that experience.

We just "trust marketing" hugely differently. That's our main difference - and that's OK.

I don't trust a single word out of marketing (& yes, I was in marketing).

I know. I know. I know. I really really really need a good smoke machine.

The problem of course is that the smoke has to be copious and yet, not harmful when deposited on cold metal inside the engine (I'm using a diesel glow plug in a can of mineral oil at the moment but it doesn't make enough smoke).

Then you need a slight positive pressure well regulated at very low single or even half-digit psi.

In summary, a good home-use

[Clare Snyder]

Warpage is defined as irregular runout without change in thickness

If it glows it can warp. I;ve seen a lot of rotors glowing red - and a few almost orange hot - - you could see the glow in daylight.

Not if thr rotor rots out under the deposits - which is VERY common

We were through all this before. It's NOT all marketing BS. You CAN get a good idea of what kind of results you will get by knowing the composition of the pads - but the friction rating basically doesn't tell you SQUAT.

You fail to get the point. It wasn't "even" wear that you would measure to determine if they required replacement. The rotors were furrowed like a ploughed field - basically demolished - before the pads were half worn - and it didn't stop worth crap.

Youi don't have to.

I told you what you were going to find out about the brakes from what you were looking at, didn't i??? I TOLD you buying brakes by friction rating was a fools errand. I told you to put OEM spec friction material on for your applicaion, and forget about trying to out-think the automotive engineers.

I don't trust "marketing" any more than you do.

I've never had one, and I've found all kinds of vacuum and fuel system leaks without. They are definitely HANDY - but not 100% NECESSARY.

Pretty pathetic excuse for a smoke generator, isn't it????

[Clare Snyder]

Try using a glycerine solution instead of the mineral oil - more fog/smoke at lower temperature. The smoke point of most oils is well over 300F - about 600F for mineral oil? Glycerine smoke machines work at about 290F IIRC.

[Arlen Holder]

Actually, I think it was glycerine. I don't remember, I lent it out and the guy returned it sans the oil. So I don't remember.

But I agree that a good smoke machine needs lots of smoke at low psi.

Sounds easy - but it's hard to find one that is ready made or *easily* converted for automotive use.

The one I made was just a new paint can with the glow plug mounted at top to the battery and a compressor plus regulator but a normal regulator is hard to get to the level of 1/2 to 2psi.

Some say a propane regulator is better - but you have to have one to know and I don't so we made do with what we had handy.

[Clare Snyder]

pick up a scrap barbq from the side of the road on one of your gas runs. Or just cut the regulator off and take it home. They are adjustable (under the cap) and are generally 7 inches of water - or roughly 1/4 PSI