Barely Passed smog.. wonder why?

[bhop]

I just got back from my smog check. Yesterday I put my stock BOV and Airbox (it's got a practically new filter in it) back on, and put in my N1 Silencer. (the car sounds so quiet, it's so weird). I left on the RRE 3" DP and 3" Cat. Last week I put on new plug wires (plugs are about 2 months old), and also had my timing belt and other belts replaced, so the engine is running very sweet right now. Probably better than it ever has.

My HC #'s were as follows:
rpm=1607/15mph - 86 (max 87, ave 21)
rpm=1768/25mph - 52 (max 52, ave 13)

All of the rest of my tests were nowhere close to the max, although higher than the averages.

So i'm wondering what would cause the HC's to be that high?

 

[bhop]

its California thats y. They are the most strictest state in the US about emissions. Dont worry about it unless u fail. could be if u have ugraded injectors or whatever else u have done to the car that u didnt take back to stock.

It's California isn't a good reason for me. Sure i'm glad it passed, but I want to know why it was only 'barely' so I can avoid it in the future.

 

[luv2rallye]

Did you put back on/replace the rear O2 sensor which controls emissions?

 

[Defiant]

I left on the RRE 3" DP and 3" Cat.

You need a real, normal, stock, functioning cataclysmic diverter.

 

[loweperf]

When diagnosing emission problems HC's by themselves is almost worthless. You need to look at the whole picture. What was the CO readings and if possible O2 readings?

 

[akdsmer]

When diagnosing emission problems HC's by themselves is almost worthless. You need to look at the whole picture. What was the CO readings and if possible O2 readings?

Also give us the CO2.....That's the efficiency indicator. Those 4 gasses tell us exactly how much fuel you have entering your engine (A/F ratio) and can even tell you if your cat's weak/bad (like lots of aftermarket cats are!).

 

[bhop]

%CO2
15mph 1607rpm - 13.0
25mph 1768rpm - 13.1

%O2
2.7
2.6

HC
86
52

CO
.15 (max .51, ave .06)
.06 (max .49, ave. .05)

NO
335 (max 701, ave 150)
77 (max 730, ave 136)

 

[94Jettameowpsst]

This isnt the best idea, but if you really wanna pass, get some type of fuel control and lean it to hell for the testing...unless you have a load dyno emissions crap thing. I live in PA and w/ it leaned out i still passed with flying colors w/ out a cat.

 

[loweperf]

%CO2
15mph 1607rpm - 13.0
25mph 1768rpm - 13.1

%O2
2.7
2.6

HC
86
52

CO
.15 (max .51, ave .06)
.06 (max .49, ave. .05)

NO
335 (max 701, ave 150)
77 (max 730, ave 136)

Ok First look at the HC readings,they're on the high side. HC's are raw fuel so this indicates raw fuel is getting through the motor unburnt. Why? Is it too rich? CO is partially burnt fuel so if it was too rich CO readings would also be high(yours could be lower but not bad).Next look at the CO2 readings CO2 is a byproduct of combustion so the higher the reading the more efficient the fuel was burnt.Yours are pretty good. That leads us to the O2 which is the oxygen left after combustion. The answer is seen here. A properly functioning cat is 98% efficient at removing HC's and CO. The cat uses the oxygen left over to burn the HC and CO so if you see O2 levels this high you know there was oxygen available to burn the HC and CO off and the cat didn't do it. Therefore the problem lies in the cat. There are other possibilities for high O2 reading (like a leak in the exhaust system) but without being there I assume you've checked for that.

 

[bhop]

I see, thanks for that feedback. I guess the hi-flow cat doesn't work as well as i'd hoped it would, although the fact that it still passed with it made it worth the price. I suppose next time, if I still have the car, i'll try to find a stock cat somewhere for the test.

thanks,
b.

 

[DSM MAN]

Don't mean to jack the thread here but, I was also wondering if you guys could help me kinda figure out whats going wrong with my car. I have been getting pretty bad gas mileage (16mpg) so I'm pretty certain I'm running rich. I know I have an exhaust leak because I have two broken studs and the lower right one near the ps pump is kinda loose. On top of that I have an egt tap and the bolt that I had to plug it up wasn't perfect. Anyway couple days ago I got a gross polluter Besides the exhaust leaks from the reading below can you guys figure anything else wrong, like bad cat (has 150k on it) Or something funky with my injectors? Thanks for all the help guys.

%CO2
15mph 1648rpm - 14.0
25mph 2636rpm - 14.7

%O2
0.5
0.0

HC
205
50

CO
.55 (max .50)
.14 (max .47)

NO
2179 (max 695)
521 (max 717)

 

[loweperf]

Don't mean to jack the thread here but, I was also wondering if you guys could help me kinda figure out whats going wrong with my car. I have been getting pretty bad gas mileage (16mpg) so I'm pretty certain I'm running rich. I know I have an exhaust leak because I have two broken studs and the lower right one near the ps pump is kinda loose. On top of that I have an egt tap and the bolt that I had to plug it up wasn't perfect. Anyway couple days ago I got a gross polluter Besides the exhaust leaks from the reading below can you guys figure anything else wrong, like bad cat (has 150k on it) Or something funky with my injectors? Thanks for all the help guys.

%CO2
15mph 1648rpm - 14.0
25mph 2636rpm - 14.7

%O2
0.5
0.0

HC
205
50

CO
.55 (max .50)
.14 (max .47)

NO
2179 (max 695)
521 (max 717)

First as an example look at your O2 readings. In your case you have high HC's and CO's but there is no oxygen left in the mixture to burn these off. So your cat seems to be working. But your definitely running rich. The first thing to do is fix the exhaust leaks. If air is getting to the O2 sensor it will make the computer think it's lean and the computer will respond by richening up the mixture to compensate. You may also want to check the timing as your NOx emissions are sky high too. If you have your EGR unhooked you should hook it back up as this will also cause high NOx.

 

[akdsmer]

Assuming that there is NO exhaust leaks which could alter the calculation, and the fact there is no real O2 present in the exhaust the air fuel ratio for this vehicle at 15 mph is 14.67:1 and at 25 mph 14.61:1. Therefore it IS NOT running rich. The CO at .55% also doesn't indicate rich. A feedback system such as this runs in this range pre-cat. HC at 205 is high precat, indicating a small mechanical/ignition misfire not due to fuel trim (which is almost perfect). NOx is definitely high. I agree with timing and EGR being looked at first. Take all of this and it equals a vehicle with low precat efficiency at idle (14.0% should be about 14.5 without catalyst), a misfire at idle and a poor (although not dead) Catalyst.

CO2 numbers should be in the low 15% range with a good operating vehicle and properly functioning catalytic converter. The O2 is extremely low, a weak cat can still use all of that up. Also, many gas analyzers do not calibrate for O2, and use a seperate O2 sensor which can be suspect, especially is you do not have access to a ambient air sample reading to verify correct atmospheric O2 reading.

 

[akdsmer]

The CO2 is not even close to good. It should be in the low 15's. This indicates engine efficiency as you indicated, but shows that there is a problem. As with any exhaust leaks, the lambda calculation can be off, but I see an efficiency problem with low CO and a slight misfire combined with a higher than normal O2 reading indicates a lean misfire condition (16.59:1 at both 15 and 25 mph-that's about 12% too lean). There is no mention in the thread as to an exhaust leak. This leaves the vehicle running lean. If indeed there is a exhaust leak than my numbers are suspect, but if not you need to find the source of the lean condition, O2, fuel pressure injectors, AFC etc....

 

[loweperf]

Assuming that there is NO exhaust leaks which could alter the calculation, and the fact there is no real O2 present in the exhaust the air fuel ratio for this vehicle at 15 mph is 14.67:1 and at 25 mph 14.61:1. Therefore it IS NOT running rich. The CO at .55% also doesn't indicate rich. A feedback system such as this runs in this range pre-cat. HC at 205 is high precat, indicating a small mechanical/ignition misfire not due to fuel trim (which is almost perfect). NOx is definitely high. I agree with timing and EGR being looked at first. Take all of this and it equals a vehicle with low precat efficiency at idle (14.0% should be about 14.5 without catalyst), a misfire at idle and a poor (although not dead) Catalyst.

CO2 numbers should be in the low 15% range with a good operating vehicle and properly functioning catalytic converter. The O2 is extremely low, a weak cat can still use all of that up. Also, many gas analyzers do not calibrate for O2, and use a seperate O2 sensor which can be suspect, especially is you do not have access to a ambient air sample reading to verify correct atmospheric O2 reading.

In this example DSM MAN states not only does he have an exhaust leak but he has several so your lambda calculation would be off. CO is always a rich indicator never a lean indicator and although I agree this reading is ok pre-cat these are after cat readings. The high HC reading could be an indication of a misfire but the lack of O2 in the exhaust would make this doubtful. Put it together with the fact that his gas milage is down and I'll stick with my original diagnosis of it's too rich.

The CO2 is not even close to good. It should be in the low 15's. This indicates engine efficiency as you indicated, but shows that there is a problem. As with any exhaust leaks, the lambda calculation can be off, but I see an efficiency problem with low CO and a slight misfire combined with a higher than normal O2 reading indicates a lean misfire condition (16.59:1 at both 15 and 25 mph-that's about 12% too lean). There is no mention in the thread as to an exhaust leak. This leaves the vehicle running lean. If indeed there is a exhaust leak than my numbers are suspect, but if not you need to find the source of the lean condition, O2, fuel pressure injectors, AFC etc.....

This example I said bad cat. CO2 reading of 13-15% is normal as you agreed in your last post 15% with a properly operating convertor so if the convertor is bad you'll lose some CO2 in the readings. The a/f ratio is on the lean side but shouldn't be lean enough to misfire. I would also expect to see higher HC levels if indeed it was going into a misfire condition.

 

[akdsmer]

This has been an excellent thread. There is plenty of good information for those who are willing to learn the byproducts of combustion and what they mean and how they affect their vehicle. I believe the differences in both loweperf and my diagnosis are in actually being present to properly diagnose the vehicle and observe the conditions when the samples were taken place. There are too many variables such as the inspection machines O2 sensors, which in most areas are not calibrated or tested as part of the 72 hour calibration (or whatever the calibration schedule is). There is also sample dilution from the exhaust system (and even from the O2 expelled from the engine) that has the inspection analyzer alter the actual tailpipe readings to compensate for. In our program area it could be a couple percent for the 2.7% O2 readings. I take all my readings in a manual mode with the sample dilution turned off for accuracies sake. Exhaust leaks, How the vehicle was run and all.

With that being, and before I start to defend myself here are the descriptions of the gasses, what they indicate and what can cause them (not my words!) so that this thread can be a learning experience for some and not just two guys bickering about nuances:

CO2- Carbon Dioxide is a measure of combustion and catalyst efficiency. CO2 exhaust concentrations increase with increased combustion and catalyst efficiency. A good running engine with a properly functioning catalytic converter produces CO2 concentrations of 15% or more.

CO- Carbon Monoxide forms when hydrocarbons are incompletely combined with oxygen. In the exhaust stream, CO is a measure of air/fuel ration imbalance occurring when there is more fuel than can be burned (oxidized) by the amount of oxygen available. CO concentrations of 1-2% measured UPSTREAM of the cat indicates a rich running condition.
CO can be elevated for the following reasons: excessive fuel pressure, leaking/dripping injectors, a cold engine coolant temp sensor reading, low O2 sensor voltage, unintended fuel entering through a faulty purge control valve, etc

O2- high concentrations of Oxygen can be caused by a lean mixture, exhaust system leakage, operation of a air injection system, or misfire. High O2 readings may result form an unmetered air leak downstream of air flow sensor, low fuel pump output, dirty/clogged injectors or a restricted fuel filter/supply hose, high electrical resistance in the injector power circuit, contaminated air flow sensor cylinder misfire.

NOX- Oxides of Nitrogen form when the combustion chamber temp exceeds approx 2500 degrees F, the ignition point for compressed nitrogen. While high NOx readings rarely accompany a rich mixture, NOx should be considered as an indicator of high combustion chamber temps, that commonly accompany high engine loads. High NOx readings may indicate: insufficient EGR flow, overly advanced ignition timing, excessive compression, cooling system faults, overly lean air/fuel mixtures, an inoperative knock sensor, low octane fuel, insufficient fuel pressure or volume.

HC- Hydrocarbons represent the many types of hydrocarbons found in raw gasoline. HC in the exhaust stream is unburned fuel. It is present in the exhaust whenever it is not oxidized in the combustion process or by catalyst action. A good running engine with a properly functioning catalytic converter should emit fewer than 50 ppm of HC from the tailpipe. Many of the best running engines will exhaust fewer than 10 ppm HC. Common causes of elevated exhaust HC include. Evap system leaks to the intake manifold. A very rich or very lean mixture. Ignition misfire or poor fuel atomization. a leaking EGR valve. Improper cam or ignition timing. Worn plugs, wires or secondary components. Uneven fuel injector delivery or dripping injectors.

In this example DSM MAN states not only does he have an exhaust leak but he has several so your lambda calculation would be off. CO is always a rich indicator never a lean indicator and although I agree this reading is ok pre-cat these are after cat readings. The high HC reading could be an indication of a misfire but the lack of O2 in the exhaust would make this doubtful. Put it together with the fact that his gas milage is down and I'll stick with my original diagnosis of it's too rich.

CO is a rich indicator yes, but entering the CO reading into a lambda calculation allows it to determine the actual mixture. Plus when confronted with extremely low CO (especially precat) it can be used to judge that it is not rich, and so is normal or low. The problem with diagnosing when you aren't physically present is that we would both likely to ID any exhaust leaks if present. Unfortunately, DSM Man didn't really say he had exhaust leaks, just broken studs, a loose stud and a funky connection for his EGT. The exhaust leak may or may not be present or in a quantity enough to really meanfully change the readings fuel control. I still have to stick with MY experience which has found that this engine makes around 14.3-14.5% CO2 without the catalyst, the catalyst converting the additional CO and O2 into the other .5+% CO2 that you get with a functioning Catalyst. I know the readings were taken post catalyst, but that doesn't mean the tailpipe readings were effected by the catalyst (IE dead cat), but once again that's just a difference in diagnostic strategy. A good running engine with a properly functioning catalytic converter produces CO2 concentration of 15% or more.

And yes, any exhaust leaks should be repaired, but especially preO2 sensor.

This example I said bad cat. CO2 reading of 13-15% is normal as you agreed in your last post 15% with a properly operating convertor so if the convertor is bad you'll lose some CO2 in the readings. The a/f ratio is on the lean side but shouldn't be lean enough to misfire. I would also expect to see higher HC levels if indeed it was going into a misfire condition

.

Again, this goes back to what both of us have seen as normal. When CO2 and CO values do not equal 14.5% or more, than I typically find a problem which needs to be addressed. CO2 of 13% indicate more than just a bad cat in my experience. If the cat was bad, I would still be seeing around 14.3-14.5%CO2. I did state a slight misfire, which can start to rise just as the vehicle starts to go lean, they just don't fall into the serious misfire category until it is leaner. I believe that we both agree on that.

With all this being said, I hope the best for b hop and dsm man. Let us know what you find out!

 

[akdsmer]

65% of passing I/M tests our state in the last 18 months show a CO2 level of 15% or more. These except one had CO under .22%

21% of passing I/M tests in the last 18 months had a CO2 level of between 14.3 and 14.9%. These typically had higher CO (between .25%-.79%)

13% of passing I/M tests in the last 18 months had CO2 levels under 14.3% (lowest was 13.3%). CO was higher (between .58 and .98%).

Just hard numbers to back up that a good, clean burning DSM's CO2 output is (usually) over 15%

 

[DSM MAN]

Thanks for all your time and information guys. I have learned a ton from this. I should have the exhaust leaks fixed by next week and my car will be legal again haha. Anyway when I get it all sorted out and the problems fixed ill post up what it was and all that stuff. Thanks again.

 

[loweperf]

I agree completely. Most people(even techs) don't properly understand emissions. I read all the time about disconnecting this and that. The thing people don't realize is with our DSM's being turbocharged we can run almost stock levels of emissions around town(also on the dyno during the emissions test) and still have huge amounts of power at WOT. Emissions are not the bad guys they also tell us that you have a properly tuned engine that is running the best that it can. As far as defending yourself,I didn't mean to offend. I was just pointing out my opinion not saying you were wrong. As you stated, the fact remains that neither one of us can properly diagnose the problem over the internet(probably good since we would both be out of a job). I would encourage everyone who reads this thread to try to learn more about the topics we discussed. It can only help you.

 

[akdsmer]

I agree completely. Most people(even techs) don't properly understand emissions. I read all the time about disconnecting this and that. The thing people don't realize is with our DSM's being turbocharged we can run almost stock levels of emissions around town(also on the dyno during the emissions test) and still have huge amounts of power at WOT. Emissions are not the bad guys they also tell us that you have a properly tuned engine that is running the best that it can.

As far as defending yourself,I didn't mean to offend. I was just pointing out my opinion not saying you were wrong.

I was just joshing about defending myself (for the most part ) I think this was a great discussion, and I think this information is valuable.

As you stated, the fact remains that neither one of us can properly diagnose the problem over the internet(probably good since we would both be out of a job).

And who wants to be out of work with $3.00/gal premium? Good posting, 'specially for making me fiqure out how to properly use quotes!

 

[RedTurboEclipse]

Sorry to bring this back up, but this seems to be the best informative thread about smog.

My beater 95 has failed smog miserably. It's basically stock, stock exhaust, just bov (recirc) and filter. Even more shocking since my other gsx with 50trim, dsmlink, etc, has passed no problem.

I don't know where to start, here are my horrible numbers. When I first got this car, it passed smog, this is the 2nd time since then. It has 140k miles original motor and pretty much everything else. Changed oil, filter, fuel filter, spark plugs and wires. Stock sensors/cat.

First number is Idle, bottom is the 2500RPM, doing AWD test no dyno

%CO2
11.3
11.3

&O2
0.2
0.1

HC (PPM)
415
293

CO (%)
5.15
5.29

haha obviously a gross polluter!

visual and other tests passed, I made sure car was warmed up.

I just put DSMLink from my other car into my daily. The front o2 is 0 at idle, and doesn't cycle if i blip the throttle. Every now and then it will actually move to .02. Never seen it go higher than .10 really. Car was warmed up. Made a log cruising, there were times where it actually cycled but hardly.

Maybe bad o2 sensor and cause for my smog fail?

I also logged the rear o2 sensor, it seems to cycle, but higher numbers, and don't know what is normal for that.

 

[toojung2die]

I just put DSMLink from my other car into my daily. The front o2 is 0 at idle, and doesn't cycle if i blip the throttle. Every now and then it will actually move to .02. Never seen it go higher than .10 really. Car was warmed up. Made a log cruising, there were times where it actually cycled but hardly.
I also logged the rear o2 sensor, it seems to cycle, but higher numbers, and don't know what is normal for that.

Your front o2 sensor isn't cycling then it's bad. You are probably getting the correct numbers from your downstream o2 but they're off because the front o2 is dead. In normal closed cycle idle or cruise the front o2 swings rapidly between .1V and .8V. The cat monitor o2 will barely cycle at all when the cat is hot and functioning. It will sit right around .1V. The high numbers you are seeing on the rear o2 is because the front o2 isn't working.

I have a RRE 3" cat that's at least three years old and the numbers I see in DSMlink are the ones I quoted. Get a new front o2 and you should be good to pass smog. DSMlink is good for more than tuning.

 

[Bubbs Malone]

I would like some thoughts on my emission results today, if someone is willing. The tech I spoke with thinks it's my over 200K catalytic converter at fault, but I'm not so sure after reading this thread.

%CO2
14.5
14.5

&O2
0.0
0.0

HC (PPM)
101
37

CO (%)
.16
.06

NO
224
381