w124 smog test shenanigans..

[JordaanDMC-12]

Hey all, my 91 300E isn't passing smog, it was due back in August, tested it twice and nothing, tried to get a temporary permit but CA won't issue me one... Had to go to Texas to get a 30 day online permit I'm planning on a move up to Alaska in 2016 and Alaska doesn't require smog tests, so I really need it to pass just once more..

For the HC (PPM)
at 15 MPH I got 158 when the max allowed was 108

and on the NO (PPM) at 15mph I got 1329 and the max allowed is 537

What would be the cause for this and where should I start tinkering? The smog tester said my catalytic is bad and they would be so kind to replace it for me for 700$... I don't know how I feel about that. The vacuum hooked up to my EGR valve isn't working, don't know if this is the cause, but I passed 2 years ago and it had no vacuum then Any help on this would be greatly appreciated!!

[oldtrucker]

A catalytic converter isn't gone until the fat lady sings.
Aside $700 seems a little high unless they put the OE in.
An after market with CARB approval should run about $300 +/-

There is a number missing, what is the CO content in your exhaust.

As it looks from where I am sitting, it may just be the O2 Sensor.
When was it replaced last time, long or short time ago?

In some cases one can simply visually inspect the O2 Sensor and determine if it needs to be replaced.
If you visually inspect the sensor, look for thick or any carbon deposits. Some people are successful in removing it by using some cleaning solvent. It may work, but you don't know if the cleaning also made the response time faster.

There are some other tests that involve other equipment, but are, in my opinion, mostly inconclusive.

A O2 sensor can put out the correct voltage, however could be slow in doing so! That's why I don't believe in DVM tests, these are good for approximate testing.

The vacuum to the EGR is only applied if the engine RPM is more than 2500RPM. I Could be wrong with the 2500RPM and it could be higher.
Simple test here, unplug the vacuum at idle and apply vacuum from some other source. If the EGR is working fine, then the engine should idle rougher.
If not, then the EGR pipe is probably clogged.

Also, make sure the smog test is performed according to book and not to a test station standard. Yes, there maybe different tests for one model that the station can do e.g. Dyno or no Dyno etc.

If the fuel ratio is getting closer to 14:1 the high numbers will come closer or below their limits anyway.
My best guess is that your CO is between 2-4% ? Just a guess.

[Duke2.6]

Search for threads under my handle using search words emission test R16/1.

There are easy tweaks that can be used to improve emissions, primarily retarding the spark advance map by shorting the R16/1 resistor and plugging the vacuum advance line.

Duke

[TnBob]

O2 sensor ohm reading should be about 7 ohms. Easy to get to the wiring in front of the passenger seat.

[JordaanDMC-12]

Originally Posted by oldtrucker

A catalytic converter isn't gone until the fat lady sings.
Aside $700 seems a little high unless they put the OE in.
An after market with CARB approval should run about $300 +/-

There is a number missing, what is the CO content in your exhaust.

As it looks from where I am sitting, it may just be the O2 Sensor.
When was it replaced last time, long or short time ago?

In some cases one can simply visually inspect the O2 Sensor and determine if it needs to be replaced.
If you visually inspect the sensor, look for thick or any carbon deposits. Some people are successful in removing it by using some cleaning solvent. It may work, but you don't know if the cleaning also made the response time faster.

There are some other tests that involve other equipment, but are, in my opinion, mostly inconclusive.

A O2 sensor can put out the correct voltage, however could be slow in doing so! That's why I don't believe in DVM tests, these are good for approximate testing.

The vacuum to the EGR is only applied if the engine RPM is more than 2500RPM. I Could be wrong with the 2500RPM and it could be higher.
Simple test here, unplug the vacuum at idle and apply vacuum from some other source. If the EGR is working fine, then the engine should idle rougher.
If not, then the EGR pipe is probably clogged.

Also, make sure the smog test is performed according to book and not to a test station standard. Yes, there maybe different tests for one model that the station can do e.g. Dyno or no Dyno etc.

If the fuel ratio is getting closer to 14:1 the high numbers will come closer or below their limits anyway.
My best guess is that your CO is between 2-4% ? Just a guess.

Thanks for the reply!

Yeah 700$ didn't sound right to me and they sounded reeeal eager to do it. I've gone back and fourth with smog, the first person we took it to didn't put it on a dyno, it passed the emissions but he failed it because he said the EGR had no vacuum. He told us to fix it and he would pass us, however, his idea of a working EGR valve was having the engine die at idle when vacuum was introduced but it just idled rough so he didn't pass it. Bought a working EGR valve online and installed it, same thing.

Went to another smog test station, said he the other guy didn't know what he was doing, should have tested it on a dyno and shouldn't have looked at the EGR valve at all as it says in the handbook my model doesn't have one (even though it's in the engine bay clear as day) this station tested it but it failed the emissions with the numbers I've given.

The CO2 measured at 15mph was 12.0 and at 25mph it says 12.0 also. The O2 was 4.0 at 15mph and 4.0 at 25mph.

regarding the o2 sensor, it's never been changed by me, and I bought the car in 2009 with 127,000 miles. Shes now creeping up to 217,000 miles and who knows how long it was on there before me I've had my check engine light come on a few times a couple years ago while driving back from Arizona, I tried to get the codes but the LED never did anything and the check engine light never came back on again after that trip, although it lights up when the key is on ACC.

I was able to get vacuum to the EGR valve, but a new problem arose from that, once vacuum built up in the system I would come to a stop, step on the gas and the car felt as though it was about to die out, then in a split second it would go back to normal. Upon closer inspection the EGR valve would stay open but close VERY slowly. I've hooked up all the vacuum lines that have always been disconnected but I noticed the vacuum line to the air pump was off, I plugged it back in to test and when I revved the engine it popped out, and the vacuum line from the air pump was shooting air out of it, it eventually stopped when the air pump stopped running.

[JordaanDMC-12]

Originally Posted by Duke2.6

Search for threads under my handle using search words emission test R16/1.

There are easy tweaks that can be used to improve emissions, primarily retarding the spark advance map by shorting the R16/1 resistor and plugging the vacuum advance line.

Duke

Will do! Thank you Duke! Thanks Bob, yeah I checked and saw the wiring was pretty assessable to the o2 sensor, is it positioned pretty easy on the actual cat, or is it in a hard to reach place?

[JordaanDMC-12]

I want to thank everyone on this thread who helped with advice and info!! Duke, I did the search and read all the research you did which I commend you for, you did a hell of a job on that write up and it was so very helpful, thank you x1000!!

I had no idea about the condition of the o2 sensor so I just installed a new one and was able to get the test done today. I shorted the resistor, blocked the vacuum and 15 minutes before I arrived at the drive thru smog station I rolled all the windows down, turned on the a/c and threw her in third gear. Not only did I pass the test, but I passed with flying colors, and not at all by the skin of my teeth.

Numbers on my failing test:

At 15 mph:
O2 - 4.0 Measured
HC (PPM) - 158 Measured, Max allowed 108
CO - 0.24 Measured, Max allowed 0.71
NO (PPM) - 1329 Measured, Max Allowed 537

At 25 mph
O2 - 4.0 Measured
HC (PPM) - 62 Measured, Max Allowed 83
CO - 0.09 Measured, Max Allowed 0.58
NO (PPM) - 482 Measured, Max Allowed 494

On my passing test:

At 15 mph
O2 - 3.7 Measured
HC (PPM) -28 Measured, Max Allowed 108
CO - 0.08 Measured, Max Allowed 0.71
NO (PPM) - 215 Measured, Max Allowed 537 <---- What a difference!!!

At 25 mph
O2 - 3.8 Measured
HC (PPM) - 55 Measured, Max Allowed 83
CO - 0.12 Measured, Max Allowed 0.58
NO (PPM) - 175 Measured, Max Allowed 494

Once again thank you so much guys, Duke you especially, you helped get my 300E back on the road!!! All your tips and advice work 110% and your research is spot on!!!

[oldtrucker]

Very good,
don't know why I had a feeling that your CO2 was higher.

They would have stuffed a new cat in and lightened you by $700!

Congrats!

[liquiddog]

Congrats! Getting my 190e to pass it's first inspection took months and three tries. I easily passed the second test the next year. Now I'm smog test exempt. Car turns 25 years old in February.

[Duke2.6]

Originally Posted by JordaanDMC-12

Once again thank you so much guys, Duke you especially, you helped get my 300E back on the road!!! All your tips and advice work 110% and your research is spot on!!!

Way back when in the early emission control era I did a MSME at the U. of Wisconsin Engine Research Center, where I did emission related research, so I am very well versed at an engineering level on how emissions are produced and controlled. As with most research, theory can provide a direction, then it's a matter of running tests and analyzing the data to see if you are heading in the right direction.

Retarding the spark advance map is a sure fire way to reduce "engine out emissions" and keep the catalyst hot so it promotes maximum oxidation and reduction reactions.

California has identified my car (and probably all M103-engined models) as "high emitter profile", and I have to go to a "test only" station.

My 190E 2.6 was getting near the limits about ten years ago, but it wasn't until I found out about the R16/1 resistor on this forum that I was able to figure out how to significantly retard the spark advance map, and it sure works like a charm to reduce the numbers and get more margin, but even I was surprised at the NOx reduction, which was about 90 percent on my car.

Retarding the spark advance map as I recommend reduces peak flame front temperature so much that very little NOx is formed during combustion, which is why the number is so low, but since so much of the fuel's energy is being dumped out as high EGT, the car will barely get out of it's own way below about 2000 revs.

I'm somewhat surprised at your high O2 levels, on both tests, but I've had tests where I was certain that the O2 equipment was out of calibration and reading way too high. I get about the same numbers as you other than O2 which is 0.0 percent. If everything is working satisfactorily including the O2 sensor and catalyst, then the O2 reading should be at or near zero. At 84K miles I still have the original O2 sensor, and it appears to be performing satisfactorily. Based on the initial test's CO readings I think your O2 sensor was okay.

...glad you got your car successfully tested, but there are still some guys who don't believe that my recommendations will have much effect and recommend fuel additives, a new O2 sensor and catalyst. Anecdotal evidence here suggests than inexpensive replacement catalysts don't last very long, so replacing the original cat should only be done if there is clear evidence that it is no longer effective.

Duke

[lsmalley]

You only have to pass the smog once then you no longer need to register it? Go pay someone some money under the table to pass your car and be done with it. Either that or register as npo until you move. These are all easier to do than dragging it out and trying to resolve something that you will never have to deal with again. I have my car registered in California in a place that does not require smog.