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  #1  
Old 10-09-2003, 01:03 PM
John H's Avatar
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Smog help needed for '86 300E

On Oct 1, 2003 N. CA implemented smog testing on the dyno. Seems I'm one of the 'unlucky' first ones whose car wont pass the new requirements. The system is so new that none of the three smog mechanics I've talked to knows what to adjust/replace to make my car pass. I'm hoping someone here has an idea.

Specifics:
CO2 is 13.7
HC is high
CO is high
NO are low

My mech's say the cat's appear OK based on the CO2. They've also indicated that the HC and CO are inversly related and reducing one will typcally increase the other. The car is very clean, HC and CO wise, on a non-dyno smog machine. I'm changing the oil and rolling in a new set of plugs in hopes a razor state of tune will let me pass the loaded (dyno) test. Any other suggestions to reduce both HC and CO under load?
Thanks!!

John H

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  #2  
Old 10-09-2003, 02:28 PM
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First, for a specific analysis it would be very helpful if you would post complete test results and limits for all three measured emissions plus CO2 and O2 on both the 15 MPH and 25 MPH tests; also whether or not your car has an air pump. (I don't think your '86 300E has one, but need to know for sure.)

Your CO2 is low! (I disagree with your mechanic.) Good mixture, combustion, and CO cleanup in the converters should yield 15.0 to 15.3 percent CO2 and no more than 0.3 percent O2 (if the car does not have an air pump).

The converters on these cars need to be HOT!!! Make sure that the car is fully warmed up with at least 15-20 minutes of in-town driving, (preferablly a five to ten mile freeway jaunt) and do not shut off the engine prior to going on the dyno. If you have to wait in line keep the engine at 1500-2000 revs to keep the converter hot. My research with an IR gun indicates that a few minutes of idle will drastically reduce converter temperature, which can bust HC on the first (15 MPH) test.

If you'll post complete test result information I can give you a more thorough analysis. I've been dealing with this loaded dyno test for several years in SoCal and have had a number of discussions with the CARB over both the test and the training/knowledge of test technicians.

Duke
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  #3  
Old 10-09-2003, 02:47 PM
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More facts

Thanks for the input Duke!

I believe the cats were hot as I did drive on the fwy and the aux fan kicked on when I was at the shop (turns out the AC was on when they ran the test - could that have made a difference?).

My mech who just tuned it up today, who does not have a dyno (there were 72 smog stations in my county and now there are only 8 with the new dyno!) ran a before and after test on his tester and there was a very slight improvement with plugs and oil change.

Here are the results of my failed test

15 MPH:

CO2 - 13.5
HC - 187 (126 max allow)
CO - 1.67 (0.79 max alow)
NO - 460 (1316 max allow)


25 MPH

CO2 - 13.7
HC - 166 (101 max allow)
CO - 1.31 (0.59 max allow)
NO - 417 (1112 max allow)

The car does not have a smog pump. Thanks for your help and assistance!
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  #4  
Old 10-09-2003, 04:41 PM
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Your CO is very high. You have a mixture problem!

The first thing to check is your O2 sensor. There have been numerous posts on this forum about checking the O2 sensor output wave form and "duty cycle" of the EHA. Don't know how good a home mechanic you are, but with a digital multimeter with a scope or duty cycle function, it's not that hard a job. The other alternative is to just replace the O2 sensor apriori (it's the most likely culprit) or find a COMPETENT mechanic who understands the KE system to do the diagnositics and repair. The fact that your mechanic thinks 13.9 percent CO2 is okay gives him zero credibility in my book.

Notice that the sum of your CO2 plus 02 is 15.0 percent. The emission control system on your engine operates by maintaining very close to stoiciometric mixture under all but WOT conditions. Native emissions out of the engine should be low, especially CO. The three way converters then reduce NOx creating free oxygen, which, along with the very small quantity of oxygen left over after combustion is available to oxidized CO and HC. With a stoichiometric fuel-air ratio there is only a fraction of a percent CO so most of the available oxygen is available to oxidize HC.

The following numbers are from the latest test on my '88 190E 2.6 last February - same basic emission control architecture as your 300E - no air pump, no EGR, just stoichiometric air-fuel ratio control, igntion timing control, and three way converters (oxidize HC and CO and reduce NOX).

15 MPH allowable (limit)

HC 113 (116)
CO 0.36% (0.74%)
NOx 261 (791)
CO2 15.3
O2 0.1

25 MPH

HC 58 (91)
CO 0.18 (0.62)
NOx 188 (730)
CO2 15.3
O2 0.0

On the suface it appears that my mixture is a bit rich, but my O2 sensor output and duty cycle are within acceptable limits. O2 sensors can drift and become less accurate over time, especially if they are not very hot. Same applies to converters. I still have my original O2 sensor (70K miles) and may have to replace it eventhough it's behavior appears to be okay.

Note that the 25 MPG emissions are better and all the O2 is consumed. This is because the converter heats up on the 15 MPH test (which has a higher relative load than the 25 MPH test) and is more efficient during the 25 MPH test.

One trick I know of is to have the car tested on a rainy day and specifically ask the tech to do the "tire drying procedure". The test procedure allows this additional step to dry off the tires prior to the loaded test when emission sampling is done. The engine is run in gear at no load for about 1 minute at about 25 MPH, but this is enough to heat up the converters and O2 sensor for higher operating efficiency.

I did this two years ago and 15 MPH HC was 87. After a thorough diagnosis I thought I would be okay, but I just squeaked by.

Next time I will go on a rainy day and ask them to run the tire drying test.

BTW, our 103 engine family has been identified by the CARB as a "high emitter family", and I have noticed that many onwers are having problems with marginal failures, even the later versions that have air pumps. Unfortunately, our emissions control system does not have as much margin for degradation as many other engine families.

The actual limits have nothing to do with the absolute standards that our cars were certified to. The field test limits are based on statistical sampling and analysis, and this is were I have argued with the CARB, especially with marginal failures.

Once you get your mixture problem fixed you will still have to watch HC.

It's basically a game we have to learn how to play! I'd like to hear a follow-up on the repair and final test numbers as I'm still researching the high emissions issues on the 103 engine family.

BTW, how many miles does your car have and do you know how many miles on on the O2 sensor?

Duke

P.S. I don't think the A/C is supposed to be on or maybe the test procedure does not specify - I'm not sure. Having it on prior to the test places a little load on the engine, which should help keep the converter and O2 sensor hot, and it will mean a little more load on the engine during the test, but it should not materially affect the emissions.

Last edited by Duke2.6; 10-09-2003 at 04:55 PM.
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  #5  
Old 10-09-2003, 04:51 PM
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Thanks again Duke!

The car has 175k and I replaced the O2 sensor about 2 years ago with a factory part. I'll try your suggestions (even pray for rain) and let you know how it turns out!
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  #6  
Old 10-09-2003, 05:07 PM
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Just spoke to the mech. O2 sensor was within spec.
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  #7  
Old 10-09-2003, 05:13 PM
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Given your high CO the tire dry test probably won't help your situation, but it will help if HC is near (or just over) the limit as in my case. If the mixture is properly controlled, engine out CO before the converter should be no more than 1.0 percent. Your CO at over one percent after the converter indicates too rich a mixture.

The first thing you need to do is check the O2 sensor output and duty cycle. Even though your O2 sensor is young, it could be the problem, If its output waveform is okay, then the problem could be the basic mixture setting on the fuel meter or the EHA or somewhere in the electronics. As our cars age, connector problems are common, so removing and inspecting the ECU and EHA connectors might do the trick. Sometimes just "cycling" connector - just removing and reinstalling them - can solve problems (old trick in the computer industry), but a thorough inspection for dirt, corrosion, or bent pins/damaged receptacles is the best idea.

Duke
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  #8  
Old 10-09-2003, 10:10 PM
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John, try a bottle of that guaranteed to pass smog stuff and let me know if it works Seriously, I'm worried about the 300SE passing smog in 8 months.

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  #9  
Old 10-10-2003, 01:37 AM
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Here are the results of the 560's enhanced test, taken (and passed) just last week, 15 and 25 MPH loaded dyno with 185,500 on the clock.

15mph:
rpm 1449
CO2 14.5%
O2 0.1%
HC 82ppm (114)
CO .14% (.74%)
NO 68ppm (1049)

25 mph:
rpm 1404
CO2 14.6%
O2 0.0%
HC 31ppm (89)
CO .03% (.54%)
NO 95ppm (879)

What I did prior to the test was change the oil the previous day. Morning of the test I drove for about an hour, about 30 minutes of that on the interstate. I left the car running while waiting my turn, figuring that would keep the cats at least warm rather than allowing them to cool for an hour. The tests were run with the AC off.

You might just want to order a new gas cap from FastLane, because the last step in the test, should you pass the smog portion, is the gas cap test. They attach the cap to a filler neck and draw a vacuum. If it doesn't hold sufficient vacuum you fail.

I notice my max values are slightly different from those already posted. Not sure if that is due to being a different engine size or locale, but they are fairly close.

EDIT: I just noticed I have two values for CO in each test. I think I forgot a "2", as in CO2 , somewhere in there. Will have to recheck the printout when I get home. 2nd edit: CO2 is properly notated.
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Last edited by MikeTangas; 10-11-2003 at 01:10 AM.
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  #10  
Old 10-10-2003, 02:09 AM
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Good numbers! Notice how that last 0.1% O2 was consumed during the 25 MPH test to lower HC and CO. The converter was operating at essentially 100 percent oxidation efficiency during the 25 MPH test - not quite during the 15 MPH test. Once all the O2 is consumed the emissions can't get any better. Your low NOx numbers indicate that the converter is reducing NOx very effectively, and the better the NOx reduction the more oxygen is freed up to oxidize HC and CO. Your NOx can't get much lower, so the limit of oxidation due to lack of oxygen has been reached. The low CO indicates the O2 sensor and KE system are in good health and keeping the mixture at the stoichiometric level.

Your CO2 numbers are low, but it could be that our new gasoline with ethanol rather than MTBE as an oxygenate has reduced the carbon/hydrogen ratio of the fuel to where the maximum CO2 is a little less than than 15 percent rather than a little over 15 percent.

The limits for the 300E and 190E 2.6 are a little higher. Because they are lighter they are allowed slightly higher proportional emissions due to less power required and less total exhaust flow. These limits keep changing based on the CARB's continuous updating of the statistical model data. You can be guaranteed that they will be a little different for your next test. The NOx limits go all over the place. I think they're still trying to figure out how to measure NOx properly, so the limits are pretty loose.

The fuel cap test is actually a pressure test to ensure that it will hold about 1.0 psi. This is a test of the car's evaporative emission controls. If the cap fails, it's probably just the gasket. Mine failed a couple of years ago, and I asked the guy to retest it. He did and it passed. It passed in February.

If your cap fails and you have to come back and have it tested, you have to go through the entire test again.

Maybe we can get the new governator to put some logic and sense into this emission test chicanery.

If anyone else has recent Califonia ASM (acceleration simulation mode - the chassis dynamometer test) emission test data, I'd like to see it.

Duke

Last edited by Duke2.6; 10-10-2003 at 02:31 AM.
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  #11  
Old 10-10-2003, 09:19 AM
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Good, old C.A.R.B.
Now there is a body out of control!

I used to attend annual Clean Air workshops, and can tell you they are the most rude and ignorant people I have ever seen.

It was so bad, after the second year, nobody would even sit with them during lunch & dinner.
What's wrong with the E.P.A. ?
C.A.R.B. is nothing more than duplication of an existing bureaucracy, that has outlived it's usefulness.
Oops, it's Friday. settle down manny.
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  #12  
Old 10-10-2003, 12:12 PM
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My measured 02 was 0.00% for both the 15 and 25 MPH tests. I assumed by being zero they weren't taking a reading. The mech said the pre-cats are not comming up to temp and are likely non-functioning so I guess that's my next step.

Duke - I asked the mech about CO2. He said it's rare for a high mileage mid-80's car w/o air injection to be over 14%.
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  #13  
Old 10-10-2003, 12:23 PM
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Dismiss air injection as a problem. The air pump operates for a minute or two on cold start to get the cats going then they're dead weight and belt drag for the rest of the trip. Once they disengage they don't contribute to the emission control process.

I'd like to know if it will help during emissions testing to leave the air pump engaged...

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  #14  
Old 10-10-2003, 02:36 PM
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Emissions Testing

Very good responses gentlemen!

To Duke-I have seen OBD-II converters get above 14.5% but rarely did I see converters that have a KE fuel system in front of it get over and above this mark. Maybe you can obtain this value with a brand new OE converter but one with mileage might be rare. Is the low NOx value on the 560 attributed solely to the catalytic converter? I was under the impression that the majority of NOx is produced during the combustion process due to high temperatures. An efficient catalytic converter can and does reduce a good percentage of NOx, but what percent? Since it is unable to reduce all NOx produced are there other methods, or devices that assist in the reduction of NOx gases? I was under the impression that a small amount of inert gas being added to the intake system would be, or is, the greatest contributor to the reduction of NOx gases because it helps lower the combustion temperature. If you feel I am not completely clear with NOx gas reduction maybe you can give some direction for some good reading material concerning "Catalytic Converters."

While I have that in mind I would like to ask any of our 380 or 500 vehicle owners who have been through the California “Enhanced Emissions” test to post their test results for comparison purposes.

I am very curious about the differences between the 116's/117's with KA-Jetronic versus 116's/117's with KE-Jetronic


To John H
15 MPH:

CO2 - 13.5
HC - 187 (126 max allow)
CO - 1.67 (0.79 max alow)
NO - 460 (1316 max allow)


25 MPH

CO2 - 13.7
HC - 166 (101 max allow)
CO - 1.31 (0.59 max allow)
NO - 417 (1112 max allow)

My experience: your CO2 is slightly low, near or slightly above14; CO value measured after the catalytic converter, near O%; the HC, 10 to 50ppm. The CO and HC are somewhat proportional, increase/decrease the CO mixture and the HC’s follow to a point at which time they will become inverse of each other.

So, high HC, CO with low CO2 indicate to me you need to confirm the engine specifications are set to a T. I suggest an O2 sensor for grins, never hurts and you may be surprised. After all these are addressed than you may want to perform a catalytic converter efficiency test. Good general automotive repair books should help understand this basic test, it works great.


Have a good weekend all!
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  #15  
Old 10-10-2003, 02:37 PM
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Quote:
Originally posted by John H
My measured 02 was 0.00% for both the 15 and 25 MPH tests. I assumed by being zero they weren't taking a reading. The mech said the pre-cats are not comming up to temp and are likely non-functioning so I guess that's my next step.

Duke - I asked the mech about CO2. He said it's rare for a high mileage mid-80's car w/o air injection to be over 14%.
Note that the CO2 reading on my car was at or over 15 percent. The 560 numbers were about 14.5 percent, and I attribute this to to the substitution of ethanol for MTBE which has decreased the average carbon/hydrogen ratio for the fuel.

The reason you have low CO2 is because you have high CO. I doubt if there is a problem with your cats. Your mixture is too rich!!! Look at the numbers for the 560, and note that CO2 is 14.6% at 25 MPH and CO is zero. If we were to richen the mixture to produce 1.0 percent CO the CO2 would drop to about 13.5 percent. The basic formula is %CO2 + %CO = 14.6. Whether the sum is 14.6 or 15.3 will vary with the carbon/hydrogen ratio of the fuel blend.

The reason you have high CO is because your mixture is too rich, and without supplemental air injection there is not enough O2 left over from combustion to oxidize the high CO that results from a richer than stoichiometric ratio. O2 is measured during the test and the reason yours read zero is because it IS zero. A rich mixture will consume virturally all the O2 during combustion and increase CO. With so little O2 in the exhaust there is not enough to oxidize the excess CO and HC.

As stated, on most modern cars that have supplemental air injection, it is only active during warmup, but that's not an issue with our cars because they don't have air injection.

From what you mechanic is saying I don't think he understands how engine out emissions change with air-fuel ratio. You need to find someone knowledgeable of the KE system and have them troubleshoot and correct the rich mixture problem that your have. Once corrected your emissions should be okay.

CO is linearly proportional to air-fuel ratio. At the typical stoichiometric ratio of 14.7:1 CO is a fraction of a percent. At 12.5:1 CO is about 6 percent. Modern emission control systems maintain the air fuel ratio very precisely at stoichiometric (except at WOT) by measuring O2 content.

At stoichiometric, 02 is close to zero, but rises rapidly with leaner mixtures. The high sensitivity of O2 sensors, their rapid response, and the sudden rise is voltage with no O2 content is what allows modern electronic engine contols to maintain an average 14:7 air-fuel ratio and control emissions with three way converters. The system runs (very slightly) rich-lean-rich-lean and crosses over the stoichiometic point several times per second as indicated by the rise or fall of O2 sensor output voltage between 0.2V and 0.8V If this control is lost the mixture usually becomes to rich and you bust emssions.

You can observe the actual waveform of the O2 sensor output with a scope, and watch it jump back and forth. If you measure it with a DC voltmeter, it should be about .45V, which represents the average voltage over the cycle.

At about 500C the O2 sensor output will "jump" at less than 0.1 deviation from the stoichiometric ratio.

Duke


Last edited by Duke2.6; 10-10-2003 at 06:34 PM.
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