ChefYota4x4

iTrader: (5)

Ok, later......

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hehehe... JUST kidding.

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First, ...THANK YOU, everyone, who lent a single word/chapter, etc., ..... I appreciate EVERY bit of input, please know that.

Secondly... As with most of these stories in the '25 YEAR OLD RIG VS. CA SMOG TEST'..., I can't be 100% sure on what exactly caused it to work out the way it did... But what I CAN say I know is what I did SINCE I FAILED TWICE........

1. Pulled off the LCE header and 2.25" exhaust and reinstalled my factory manifold and collector to CAT pipe
2. Installed new Magnaflow Factory Size CAT(why I said I can't be sure)
3. Left the timing at 5*BTDC
4. Verified NO OBSTRUCTION, whatsoever, within the EGR system(leaving only 'failed this or that' as the only alternative).
5. Used the same 02 Sensor I failed with last time(He said it might indeed be a lil lazy, but it's working better where it is now, for sure.) This put the 02 back on the manifold, btw... and shortened the wire by around 18", back to it's stock length.

What I ALSO know, for a fact.... When I got done driving like a banshee with the header on(to warm up the CAT for the tests I failed), the EGR tube, even after a romping at high RPM, was NOT hot. THIS time, after driving around and pulling in there, with the stock exhaust manifold on there... it got nice and hot(the egr tube). My point being, ... I think the new CAT had a lot to do with it(even though the other one was NEWER)... But I really believe the limiting of the EGR(by backpressure and flow passages) was causing some of my High NOX problems.

** funny tid bit** .... I'd forgotten that, when you are running right, the machine will wind up and just shut off if it's really clean.... He ran it for around 10 seconds and it read, "FINISHED".... I kinda freaked out, and then he said, "NO, that's good... YOU PASSED... When it cuts off that early, it's because it's really clean and there's no point in putting another 80 Seconds of pollutants into the air just to prove what the machine already sees"... FHEWWWWW! hahaha. In fact, it jumped from the 15mph part to "now 25mph" part in 10 seconds.. then jumped from 25mph to finished in just another 10 seconds... WOW, what a great feeling to be done with this, at least the 'worry bout the tags' part. I know, I could have paid and got a temporary... I would have if necessary... But I feel better having refused to settle and put it off another few months, lol.

It IS much quieter... But it still has a nice throaty/thud to it.

I will be keeping an eye on my mileage, but furthermore, I'll be adding some testing in the near future. I HAVE TO verify that my Fuel Pressure Regulator is working(just for my sanity/to rule it out or verify), because part of even these readings contradict each other to a point. So, that's one of the first things.... But also, having ANY 02 in that reading at all means 'air is getting in', somehow... So I'll be doing a healthy shakedown of my throttle body idle/air screw(to see if I'm actually pulling in air THROUGH the screw, etc. And then I'll be going from there, on whatever I'm tols are the obvious culprits to a lil bitty puppupup-------pup--------upupupupup type missing. (Far as the missing... the smog dude told me, "Mark, you have, MAX, a 5rpm out of 1500 and 2500rpm jump, either way.. That almost always rules out a miss."... He also explained that doing propane testing on an 02 sensor is 'ok', but to really read it properly I need an oscilloscope.

rworegon

Congrat!!!!!! Great job! Those NOX numbers dropped like crazy...... I like the O2 sensor value sketch too. :-)

Grego92

iTrader: (4)

yota721

i dont know if i missed somthing, but i thought you had a lce header?

ChefYota4x4

iTrader: (5)

Hehehe... I know. I can't believe the 'exhaust' change had nothing to do with it... I can LITERALLY, physically feel the difference in heat in the EGR tube-to-plenum when 'racing the motor for longer periods'... Could NOT get that out of it before that.

WOOT, domo dance! hehe. Yep, I was ECSTATIC ..... after he explained to me why he stopped so fast! ... wont lie, .. as I said, I was scareeeed at first! hahaha.

I DO have an LCE header... Been posting quite a bit here and on a smog thread I started, ...'how the LCE header and my 2.25" pipe from there to the back might have had SOMETHING to do with my lack of backpressure(adequate to operate the EGR anyhow) and MUCH else, lol.... I still have the header... just running stock manifold to 2" to CAT, 2" to Muffler to 2.25" out the back, for now. It's NOT that big of a deal to change it back... And I may do that eventually.. But for now, I'm running like this to rule out/verify, etc., a few things that are concerning me.

rworegon

Chef, you know what 4Crawler said about the EGR being barely adequate.....it needs all the help it can get.

The lack of backpressure seems to have a lot to do with it.....you know the gases are flowing now that that EGR tube is getting hot. Also, the other CAT may have been wonky too.....

ChefYota4x4

iTrader: (5)

RIGHT, and it helped to really get that VISUALLY DOWN in my head! You know, 'written on the tablet in my cranium'? lol. It helped to make sense of how SIMPLE it really is... And yet, it might just be TOO simple in some ways..

WIMean is, .... clearly I COULD HAVE learned if my CAT was bad if I had 2 -O2 sensors, ya know? lol. That's SOMEWHAT/largely what the second one is for. First one reads and sets air/fuel... Second one READS, well, 'is the CAT workin?' lol. "How much", anyway. But with mine, having no EGR sensors... You basically run through a bunch of 'KIND OF telling' tests, then clean it if they're 'iffy', then toss it if you can't figure it out?? hahaha. I KNOW, at least I think I do, lol; That EGR is working WAY better than it was. And EGR controls what? NOX! So, yes, in theory, the CAT must have cleaned up a lot of that.. but I KNOW it wasn't all of it. A combination of things, if you will?

Yes, I believe the CAT was 'half working', as the Smog Tech said.

And yes, ...those were his notes on my page explaining how fast the 02 cycles(MANYYYYYYYYYYY per second), and how it's best to have an oscilloscope to just see once and for all what all is working and what is not? lol.

ToyoTech559

good job. when it comes to emissions stuff. i try not to mess with them too much. if the aftermarket parts put certain things like the o2 in different spots than factory. its never good. if you had to extend that o2 sensor for the location is not good as well since more wire means more resistance = wrong valve sent to ecu. should always run an OEM cat, they cost more but theres a reason for that. having an original cat with 220xxx at the time when i smog my runner and pass says something about factory cats.

RMP8080

Well Mark, I learned two things. 1. Passing smog test or a real pain and 2. Didn't move to CA....lol

Great job on the o2 thing, thanks for posting............Bill

ChefYota4x4

iTrader: (5)

Yeah, .... I was warned, many times, by many Guru's, lol... Had to 'run with the cool parts fever'! lol. Not knocking the header, ... it's a good product. I'm sure if I had an 88 or later, I'd have passed or come closer, or at least known that the CAT was 'iffy'? Smog guy said, "this is dramatic... can't just be the CAT, especially with the same 02... I BET moving it at least helped". He said to slap on the header some day again and put the 02 in the header itself, then stop into a scope shop and have them read it for me to see. For now, I'm good, ya know? Just too exhausted and overwhelmed.... Gonna try to get away for a weekend or something. NEED IT! Need to see my pops, to, so might kill 2 birds with one stone kinda thing, ya know? I NEED IT! ...did I say that? hahahaha. Heck ,maybe pismo?

Hey, see? It WAS NOT all for nothing then, right? hahaha.

RMP8080

Mark, how about this?

Chef Mark's on-line Yota Tech SMOG CERTIFICATION COURSE, classes are limited so act on
Call 1-888-555-1234 or on-line @ www.chefmarksmogclass.com


This is the combination of three sub-modules of study. It includes the BASIC California Bureau of Automotive Repair (BAR) certified course of study (which includes information on basic smog inspection, laws and regulations pertaining to smog inspections, and how to perform a proper smog inspection using the BAR-97 smog machine in basic mode); the OBD-2 diagnostics (which includes advanced training on how to diagnose and repair today’s OBD-2 type vehicles using the latest high-tech diagnostic test equipment); and the BAR’s 2012 smog update (which includes the latest information on rules and regulations of the current CA smog program) courses.

Terrys87

iTrader: (1)

A big CONGRATS!! I am sure that was a big relief. I know you were pulling your hair out on this and dont know if there is any left to pull out now, but still you had to be jumping up and down for joy. Maybe this will help your poor mileage also.

I am guessing that for the most part your O2 sensor was just too far back and maybe the catty was some problem. The fix is normally the easy part, the troubleshooting, not so much.

Just curious, with the LCE header, did it really make much of a difference. I run the cheapy Pacesetter header and really dont notice any difference. Always have a problem
getting them to seal up and a little louder. Just a cheap way of getting around a bad manifold.

Congrats again,

ChefYota4x4

iTrader: (5)

HAHAHHAA.... That really made me laugh, man! In a short response; HARDLY, but thanks ... And NO THANKS! hehehe.

The funny thing is, ...there is only so far you can go without an oscilloscope/etc. I should have thought about having a 'pre-and-post CAT reading done right off the bat... But I was thinking, 'WHY? IT'S NEARLY BRAND NEW!'..... well, now I know, 2 years on a CATCO that's been through a HG failure and LOTS of "lean, rich, lean, rich, lean, rich"-schizophrenia.... Well, it's NOT new! hhahaha. The exhaust guy(been there 30 years), said "Don't think it's toast... But the temps it was getting/HG failure/etc. ... just wasn't 100%. That, along with the 02 being moved, etc... it might have changed things just enough to confuse the ECU and cause it to ALWAYS return to(or go in and out of open-closed) the same setting, thinking it's SUPER rich or lean. Whatever it is, IF THERE IS something still lingering.... find it, or you'll go through another CAT, fast!"....


Actually, I am down to help ANYONE who needs it in chasing down some answers. But see, that's the thing... 0BD2 guys?..... My advice? GET A CODE READER, NOW! lol. Seriously.... the CRV threw a code in Laughlin, NV..... walked into Auto Zone, ... guy came out.... plugged in, .... 5 seconds later... "02 FRONT BANK, PO3187998-WHATEVER" lol..... NOW, when it says, "02, REAR BANK".... what's that gonna tell me, Bill? CAT, exactly. STUPID YEAR DIFFERENCE! hehehe. JK, ..... but really, it would have helped. For the smog guys, they say, "actually, these are easier... The others mislead and have so much more to check/etc. And the limits are WAY more strict, just a couple years later".... Still... having 14Codes that all have four variables each... YEAH, fun! lol. Just a matter of P.O.E., that's the best way, as Roger and many others taught me(Andy, Scout, Fleckster!....YOU ROCK! lol).

I'm going to FINALLY do a smoke test... The guy doesn't have time right now, but soon. (FREE)<<< lol.... Seriously, WHY NOT rule out any vacuum/unmetered air intake, right? I AM letting OXYGEN out the pipe, .... so it's coming in somewhere. Can't find it with conventional means, so time for 'the Smoke', ya know?

Also gonna try what RW said, and run a couple gallons, see what she's getting.... Then switch 02's, to the new one, reset the ECU and then check again......(Smog Repair guy said he's seen a few 02's that have been through HG failure and run lean/lazy too long/too HOT too long... get really wonky).... So being an easy and unharmful experiment, WHY NOT, RIGHT? hahaha.

SERIOUSLY, YOU GUYS, ...thanks for all the help/patience/time you give me!!!!

xxxtreme22r

Dang Chef, I woulda had this fixed by now.
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By moving far away from CA.

ChefYota4x4

iTrader: (5)

Hahahaha... ahhhhh lol. I know, ..... I know, it's bad in many ways... But WOW, Brandon... when you 'get out there' into the CA wild? INCREDIBLE and unique in all it's ways... I bet you're gonna say, "YEP, I'm sure it is... So MOVE and then visit!" hehehehe. Almost took a job in OR(no smog where they were, near Bend).... And once in TX, I worked in Houston opening a restaurant... (think it's less crazy there, too?) ... Then in Iowa, ....WOW, WAY too humid and hot in the summer for me! lol(99% humidity and 100*F !!!!) .. But alas, my kids and family needed me ,....so I stayed. DANG FAMILY! hehehe. I would love to move, at least for a while, back to AZ... I reallyyyyyyyy loved living and working there. (right to work state, baby! "Yeah, ummm, buddy? YOUR FIRED!".... "WHY?" .... "CUZ, now leave", hahahaha). Their smog is pretty crazy now too, however... GRRR! Everyone follows CA, that's the problem. 'EVENTUALLY' I should say. Although lately? Yeah.... some 'good'ole'states' been fighting off the 'CHANGE' pretty hard... I'm proud of em! lol.

In short... YEP, THE BUREAUCRACY STINKS! lol.. The place is beautiful.

ChefYota4x4

iTrader: (5)

While I'm happy I passed.... I have to wonder what's going on;

I recalculated my LAMBDA #'s with the new results;

15MPH= 14.97;1(or Lambda=1.018) 25MPH= 14.87;1(or Lambda=1.01)

This has me curious as to whether I 'FIXED' or 'CHANGED' anything by returning to stock exhaust. I know it had to 'effect' things, to a point.. But if 'SOMETHING' within the motor(Vacuum Leaking/Bad or dead spotted AFM/ Same 02 that might, at this point, be not up to par/ECU issues/Wiring issues/WHATEVER) is causing it to constantly revert back to this 'LEANER' mixture... I can't be content with that. I will know more when I see the mileage off this tank...... But the LAMBDA, from what I read, is VERY telling.

Also, this new CAT; It's already GOLD in hew. Not rainbow colored like the last one..But nonetheless, I can't seem to find 'CAT indication/Coloration Pictures'. The last thing I want, however, is to ruin YET ANOTHER brand new CAT via "A/F mixture being 'OFF', etc.

I might just take her in and have a smoke test done(to rule out, once and for all, the air getting in some how)... and will probably swap in the new 02 as well.

As I stated to RW... I DID NOT reset the ECU after moving everything around/cutting the 02 wiring and redoing it.. etc. I was rushing and forgot. Thinking that might not matter much since it's the same 02 sensor(even if it IS reading a LIL faster, etc.) ???

Sorry, don't mean to drag this out, AND TRUST ME, I'd rather not be bothering/having to bother! lol. I just want to get the A/F mixture right and be done with it!

ANY thoughts on what I've posted above? Thanks!

toyospearo

Dang that seems complicated.
I spent yesterday pulling a 93 22re out of a friends rig. One of the wrist pins on the piston gave way and grenaded his piston. Literally schrapnel everywhere.
New motor goes in tomorrow!

Terrys87

iTrader: (1)

I dont have any suggestions for the above, but you said on your earlier post about having Oxygen still getting and through the pipe.

I am guessing maybe not all oxygen gets burned during the combustion or maybe it does. Guess high tech equipment could tell. I just assumed it did. Is there some way to tell Oxygen entered the system after combustion? Which would leave me to believe some where after the exhaust manifold all the way to the end of pipe.

ChefYota4x4

iTrader: (5)

Yeah, ....it SEEMS that way, at first, lol. The complicated part is trying to figure out WHICH item/s are malfunctioning without throwing a code! lol. Meh, ... I'll figure it out, eventually.

Well, he explained it as "oxygen getting through is a sign of incomplete combustion.... Oxygen should burn off with the proper air/fuel mixture"..... does that make sense? MOSTLY does to me, kinda-sorta-maybe, lol.

I'm not sure HOW exactly they do so, but I'm pretty sure they can figure out anything if you want them to fish enough, right? hahaha... Before and after measurements.... Hmm, I suppose that IS a tricky one, lol. The REAL important trick is to CONCLUDE the Air/Fuel Ratio to the tee...They can also rule out EFI Components completely by running the entire fuel system on propane for a bit with the fuel pump disconnected/certain things jumpered. Using Propane/NO EFI/The guy concluded last time that my issue/miss was mechanical. I can see the valve lash being a problem in some cases(regarding smog, etc.), but I would bet dollars to donuts after 15 times in a couple years I have it down pretty well? lol. My guess is still something within those elements that Roger mentioned: "AFM/02/ECU determine A/F Ratio".... So, I'll just keep my eye open for some 'swap in' stuff's to borrow, etc. Can't hurt anything to try, right?

The "spare" ECU thing would be good... Same with Ignitor/Coil/Wires/Plugs/...........hahaha, etc., etc., but I would like to avoid spending anything on parts, for now, ya know? Pretty extensive testing available on that stuff. I have a buddy who might have an ECU from a wrecked 87 4WD EFI PU... Would work I suppose.... Problem is getting a hold of him, lol.

And, after all, ....what is an Oxygen Sensor Sensing/Trying to eliminate?

Interesting read; http://www.916smog.com/smog-help.html

I STARTED at really looking into AFTER #5, where it starts talking about ''IF YOUR LAMBDA IS ABOVE THE IDEAL, 14.7;1....". BUT, I can see why the smog guy was a lil confused, as some of my results seem to contradict rational. How could it read rich and lean at the same time? Too much heat? Too much Air getting in unmetered? WHAT, WHAT I ASK YOU? hehehe. JK, but really, it was a great read IMHO.. really worded well I want to stop by and discuss the O2 reading stuff again with him... Just to learn more, ya know? I might not be explaining. Anyway, enjoy the read, if you want, lol...>>>


So you just came in to get a smog inspection and your car failed. It's not the end of the world. We are here to help. We want to see your car pass the Smog Inspection just as bad as you do. Let start by explaining the 3 different failures.

1. Visual inspection: These items are listed in the middle of the page under "Emmissions control systems". This is just a list of the components that are supposed to be installed on your vehicle. The Pass/Fail/ or N/A result is just a record or the device being present or missing. So just because it say's "Pass", does not mean the item is functioning properly. If all the visual results are "Pass" or "N/A" then you have passed the visual portion of the test. The other items under visual inspection that are labeled "Functional" are part of the Functional Test.

2. Functional inspection: This part of the test is a record of a test procedure done in the Smog Test. So this Pass/Fail N/A result is differentthan the visual result. If they all say "Pass" or "N/A" then your vehicle has passed this portion. These items include Timing, Egr, Evap, Check Engine Light, OBD2, and Gas Cap Test.

a.Timing: If your vehicle failed the Smog inspection for timing you will need to have your timing adjusted. WARNING! After changing the timing, your Emmissions WILL CHANGE. Sometimes they will get better sometimes worse. If you advance the timing N.O.X. & H.C. inharently go up. If you retard the timing they go down. There are variables to this rule, but this is usually how it works.
b. EGR stands for exhaust gas recirculation. This system is usually not tested in the smog inspection. This system does cause alot of cars to fail, but this item will be covered in "Emmisions" portion of this information.
c. Evap is a system. It is a bunch of different components installed that make this a system. These consist of a gas tank, hoses, a charcoal canister and valves or switches. If your vehicle has failed for EVAP, then our test has indicated your system has a leak. This could be a simple hose all the way to a leaky O-ring on top of the tank. It is very difficult to pin point a Evap leak without having a Smoke Machine. These systems are usually a resonably price to repair and should be repaired by a repair facility that has the appropriate equipment (Smog Check Test and Repair Station)
d. Check Engine Light is the light on your dash that usually say's check engine, pcm, engine or has a picture of a motor. There are many different kinds. If this light does not come on it fails the functional portion or the smog inspection. If it comes on but stay's on then it fail's the smog inspection also. This light is an indication there is a problem with your emmisions system. This does NOT mean the computer is bad. In 20yrs as a technition I have replaced less that 20 computers (ECM) in vehicles. They normally do NOT go bad. Usual cause is a sensor out of range, or a disconnected wire or ground from previous repairs. My recomendation to fix this problem is find a licenced Smog Check repair facility. Approx 98% of our 2nd attempt failures are from people taking there cars to "shade tree mechanics". I see people spend more money getting their car fixed at home than at a shop. Most repairs are under $500 at a licensed Smog Check Station.
e. obd2 is only applicable if your vehicle is a 1996 or newer and is done by plugging in our machine to your obd2 data port. After it is plugged in, it reads the Monitors and any fault codes. The vehicle has several different monitors. One for each different system. There is usually not a problem with this test as long as your check engine light is not on, your mechanic has not erased or resest the computer, and you have not changed the vehicle battery recently (approx30 miles).
f. Gas Cap is self explanitory. If the gas cap is bad we will tell you and sell you a new so you can pass the Smog Test. Some stations fail you and then charge you for the gas cap and another Smog Test Inspection.

3.Emissions:
General Background

Concentration of combustion products in the vehicle's exhaust, most of which pollute the air, give important diagnostic clues to the vehicle's engine efficiency. The component gases which contribute the most to air pollution are hydrocarbons (HC), carbon monoxide (CO) and oxides of nitrogen (NOx). This is not N2O (NITROUS). Three of the five gases measured at the tailpipe are regulated pollutants - HC, CO and NOx. The remaining gases, oxygen (O2) And carbon dioxide (CO2), while non-regulated, play a significant role as diagnostic aids. THe 4 gas analyzer measures HC, CO, CO2 and O2 concentrations. The five gas analyzer (BAR 97) adds the measurement of NOx as well.

The exhaust gas analyzer is a highly versatile and accurate test instrument. In addition to testing carbon monoxide (CO), carbon dioxide (CO2), oxygen (O2), hydrocarbons (HC) and oxides of nitrogen (NOx) (5-gas version) for repair requirements or after a tune-up, it can be used to assist in detecting and locating, fuel, exhaust, emission control and engine service problems. Following are a few general facts to keep in mind when using the gas analyzer:

1) High Carbon Monoxide (CO) readings usually indicate a fuel mixture richer than ideal (rich mixture - air fuel ratio below 14.7). In general CO is an indicator of combustion efficiency. The amount of CO in a vehicle’s exhaust is directly related to its air-fuel ratio. High CO levels result from inadequate O2 supply needed for complete combustion. This is caused by a too rich mixture - too much fuel (AFR readings below the optimal 14.7, Lambda below 1.0). If your vehicle failed the Smog Inspection and has a high C.O. level, This should always be fixed first. Circumstances that can lead to high CO emissions:

* Improper float settings in carbureted vehicles

* Dirty or restricted air filters

*Excessively dirty or contaminated oil

*Saturated charcoal canister

*Non-Functioning PCV valve system

*Improper operation of the fuel delivery system

*Improperly functioning thermactor system

*Catalytic converter intervention and CO concentrations
High CO readings at the tailpipe are an clear indication that there is a problem in at least one part of the system, but an CO reading that appears within "normal" ranges or is only modestly elevated is not necessarily a reliable indicator of proper or even acceptable system performance. Low range C.O. readings are possible, and not uncommon, from a malfunctioning engine equipped with a properly functioning catalytic converter. In such circumstances, truly elevated pre-catalytic converter CO levels will be masked by the catalytic converter and the potential for a CO problem must be further evaluated in the context of other readings of abnormal gas concentrations and AFR / Lambda readings.

2) Normal CO readings. If the combustion process is succeeding at or near the stoichiometric point (AFR equals 14.7, Lambda equals 1.0), C.O. levels during an idle test will typically measure less than 1% Pre-Catalytic Converter.

3) Low CO readings. There is, effectively, no reading for CO that can be characterized as too low or "below optimal". CO concentrations will appear "normal" even in a lean burning environment, where AFR is above 14.7 (Lambda is above 1.0).

4) High hydrocarbon (HC) readings usually indicate excessive unburned fuel caused by a lack of ignition or by incomplete combustion. ALWAYS FIX CO BEFORE HC. Concentrations are measured in parts per million (PPM). Common causes include a faulty ignition system, vacuum leaks, and fuel mixture problems. Circumstances that can lead to a high HC emissions are:

* Incomplete combustion due to fouled spark plugs.

* Improper timing or dwell

* Damaged ignition wires

* Low compression

* Vacuum leak

* Ineffective or faulty air management system (ECM control of air/fuel ratios)

* Catalytic converter intervention and HC concentrations
High HC readings at the tailpipe are an clear indication that there is a problem in at least one part of the system, but an HC reading that appears within "normal" ranges or is only modestly elevated is not necessarily a reliable indicator of proper or even acceptable system performance. HC readings at or near "normal" are possible, and not uncommon. From a malfunctioning engine equipped with a properly functioning catalytic converter. In such circumstances, truly elevated pre-catalytic converter HC levels will be masked by the catalytic converter and the potential for an HC problem must be further evaluated in the context of other readings of abnormal gas concentrations and AFR / Lambda readings.

5) Oxygen (O2) readings. Oxygen, measured as a percentage of the exhaust volume, reflects the amount of gas remaining in the exhaust sample after the combustion process has taken place. Ambient O2 readings should be about 20%, reflecting the natural amount oxygen found in the air. The ideal range for vehicles without a secondary air injection system is less than 1.5%. If there is an air injection system, O2 levels will typically fall n the range of 3% to 4%. Pinching off the air hose of a vehicle equipped with air injection should produce O2 levels similar to those found for vehicles without air injection.

6) High oxygen (O2) readings indicate too lean an air-fuel ratio (AFR higher than 14.7, Lambda greater than 1.0). Circumstances that can lead to high O2 emissions are:

* Lean fuel mixture (AFR above 14.7)

* Vacuum leaks

* Ignition related problems causing misfires.

7) Low O2 indicates a rich fuel mixture (AFR below 14.7, Lambda below 1.0).

8) High carbon dioxide (CO2) readings indicate a nearly ideal air-fuel ratio and efficient combustion

9) Low carbon dioxide (CO2) readings indicate a fuel mixture either too rich or too lean, exhaust system leaks, or sample dilution.

10) Oxides of Nitrogen readings. Oxides of nitrogen (NOx), including nitric oxide (NO) and nitrous oxide (NO2), are formed if the combustion temperatures within the combustion chamber exceed some 2,500 degrees F. This can occur when the engine is under load. When excessive temperature conditions exist, the greatest amount of NOx is typically produced at the stoichiometric point (AFR 14.7 or Lambda of 1.0) as the engine is under a light load. If the combustion process within an engine is burning fuel at or near stoichiometric point, NOx levels on acceleration will typically read significantly higher than those measured at cruise and during deceleration. Typically, the NOx readings at idle will be 0 PPM.

11) High NOx Readings. Circumstances that can lead to abnormally high NOx emissions are:

* Malfunctioning EGR valve

* Lean fuel mixture (AFR above 14.7, Lambda above 1.0)

* Improper spark advance

* Thermostatic air heater stuck in the heated air position

* Missing or damaged cold air duct

* Combustion chamber deposits

* Malfunctioning catalytic converter

* Catalytic converter intervention and NOx concentrations
High NOx readings at the tailpipe are an clear indication that there is a problem in at least one part of the system, but an NOx reading that appears within "normal" ranges or is only modestly elevated is not necessarily a reliable indicator of proper or even acceptable system performance. NOx readings at or near "normal" are possible, and not uncommon. From a malfunctioning engine equipped with a properly functioning catalytic converter. In such circumstances, truly elevated pre-catalytic converter NOx levels will be masked by the catalytic converter and the potential for an NOx problem must be further evaluated in the context of other readings of abnormal gas concentrations and AFR / Lambda readings.

12) Low NOx readings. There is, effectively, no reading for NOx that can be characterized as too low or below optimal. NOx is naturally 0 ppm at idle. NOx concentrations may appear normal even in a rich burning environment where the AFR is well below 14.7 (Lambda below 1.0).

TOP

Facts to Remember

The byproducts of combustion are dependent on the air-fuel ratio.

13) O2 combines with HC to form CO2 and H2O.

14) O2 combines with CO to form CO2.

15) CO is an indicator of air-fuel mixture richness.

16) HC is an indicator of fuel mixture leanness (or richness) and misfires.

17) CO and O2 are equal at the stoichiometric air-fuel ratio.

18) O2 and CO2 are indicators of exhaust system integrity, sample hose and probe integrity, or both.

19) CO2 is an indicator of combustion efficiency that peaks at or near the stoichiometric air-fuel ratios, and decreases with lean or rich air-fuel ratio.

20) Air injection systems dilute the exhaust sample with O2.

21) O2 is essential for proper operation of the catalytic converter. Its concentrations are essentially unchanged by the catalytic converter, providing a "window" through the converter to the engine. O2 levels are higher on vehicles with properly operating air injection systems.

22) If CO goes up, O2 goes down (inversely related)

23) If O2 goes up, CO goes down (inversely related)

24) With the air injection system disabled and the CO above 1%, the catalytic converter is oxygen-starved. Without O2, it does not fire, allowing exhaust concentrations to be more like readings taken ahead of the converter.

If readings are within the manufacturer’s or local/state/federal allowable limits, it can generally be assumed that the fuel, ignition, and emission control systems are functioning properly. If they exceed the limits, repairs or adjustments are probably called for.

ChefYota4x4

iTrader: (5)

Reading 6 and 7... I can see why the guy is thinking, "HUH?"... LOW 02 could mean Lean mixture or HIGH lambda... HIGH 02 from LOW lambda? hahahaha.

But actually, this is saying that "HIGH 02" would be over 1.5% for non air injected systems, like mine.... So if my 02 is low, why is my LAMBDA ABOVE 14.7? Hmmmm.. What is it that Elmer Fudd says? "Something weawwy skwewy going on hewe"! lol.