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

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

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!

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.

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!

Just spoke to the mech. O2 sensor was within spec.

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

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.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

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.

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

Good, old C.A.R.B.
Now there is a body out of control! :eek:

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. :D

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%.

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...

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

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!

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

Duke,
The 02 sensor has one long, thin connector and a separate 2-prong connector. Could you please explain how the probes of the digital multimeter set to DC voltage should be applied in order to properly take the measurement.
Thanks

The two pin connector is the O2 sensor heater. Disconnect this connector and measure the O2 sensor heater for continuity. It should measure a few ohms. With the engine running there should be 12V on the chassis harness side. Continuity of the heater and 12V on the input harness means the O2 heater and power supply are okay. On my '88 the heater is on all the time, but on some heated O2 sensor systems the heater may only be on during warmup.

The single pin connector is the O2 sensor signal. If you pull the connector apart just enough to attach a small test lead or probe from your voltmeter or scope to the pin, you can eavesdrop on the O2 sensor. Connect the meter or scope ground wire to any convenient chassis ground or the battery negative terminal to be absolutely certain that you have a good ground. A DC voltmeter should show about 450 millivolts.

If you have a scope you can juggle the time and voltage scales until you get a good image of the voltage waveform, which should jump between 0.2V and 0.8V several times per second.

If the readings are not as above, then you have either a bad O2 sensor or there is a problem somewhere in the control system. For example, if you disconnect the EHA connector, the system will default to "open loop" operation, which should be a bit rich if the basic mechanical mixture adjustment on the air meter is in the proper range. This will cause a high voltage reading on the O2 sensor or a constant high voltage reading on a scope.

Duke

Thanks Duke. You made it pretty clear. One follow-up: Are any special tools needed to remove the sensor from the exhaust pipe? I've seen something advertised on Ebay as such a tool.

I've never removed the O2 sensor from my 190. They usually have a big hex, but sometimes access can be tight. Also, they tend to seize, so be sure to use a good high temp antiseize compound when installing a new one and don't overtorque it.

Duke

Re: Emissions Testing
 

CO2 readings are a funtion of the fuel blend. In my test last February my car was over 15 percent, but with the new CA fuel that substitures ethanol for MTBE CO2 levels are lower because of the lower carbon/hydrogen average ratio of the fuel. For example, straight run gasolines averages C8H18, but methane (natural gas) is CH4, so methane will produce less CO2 and more water vapor than straight run gasoline.

The equation %C02 + %CO = xx, where xx is the percent CO2 with complete combustion (zero CO), and this will vary with fuel blend.

NOx is created in the flame front, which reaches about 4500 degrees F. There are two practical ways to control the amount produced during combustion. One is to retard timing from optimum and the other is to dilute the fresh charge with an inert gas, which is what EGR does. Both of these strategies reduce peak flame temperature, but this reduces thermal efficiency, which reduces fuel economy. Rich mixtures, such as what occurs at WOT will also reduce NOx to very low levels, and there is little at idle. Most NOx formation occurs during steady state cruise.

Heavier cars are more likely to require EGR than lighter cars. In order to meet the absolute certification standards in grams per mile, which are the same for all cars, a heavy car will have to have lower proportion emissions than a light car. Final NOx values after the converter depend on having the correct exhaust gas composition and converter efficiency. I don't have a good feel for how much reduction of NOx occurs in the converter. In the several ASM tests I have had on my two modern cars with three way catalysts, the NOx measurements and limits are all over the place. This is why I think the CARB is still trying to figure out what they are actually measuring.

Duke

Well, with a tune and a new cat I'm almost there. Here's the new #'s

15 MPH

CO2 - 14.2
HC - 132 (126 max) failed
CO - 0.9 (0.79 max) failed
NO - 305 (1316 max)


25 MPH

CO2 - 14.5
HC - 72 (101 max)
CO - 0.4 (0.59 max)
NO - 366 (1112 max)


Like I said earlier, we've gone from 72 shops to 8 so I have a MB tech comming to the dyno shop after hours next week to do a 'tweak' and get those 15 MPH #'s down. Thanks all for your help and explainations, especially Duke! After this experience I don't think I'll ever sell my smog exempt fords.

John - Did you ever run your Shelby with COCOA at Willow Springs? I used to run my Cosworth Vega with them in the eighties until Lynn Park got so many entries that he limited it to Ford powered cars only.

Duke

Richard,

Not sure if your car takes the same O2 sensor as the 560, but the 560 only required a 22mm box wrench. Many folks will simply cut the wire to the old sensor, remove then feed the wire to the new sensor through the box wrench to install. I found it easy enough to feed the wire through the wrench prior to removal, allowing me to bring it out in one piece.

smog test so cal area
 

This is about cars that pass loaded mode smog checks. Being a former bay area smog tech,now so cal. area. San diego. i find that test results on cars that pass do not reflect that cars best smog numbers.The old test ran the car for the full test then gave it a second chance to pass if the car was failing. This new test will only test long enough to get passing numbers, then switch to the next part of the test. this will give passing numbers but will not give the best numbers that the cat can produce with a full time test. also german gas caps almost always fail.even on 5 year old cars.I test these caps twice and they will pass most of the time.ask the smog tech. GREAT FORUM

Duke

The shelby is an ex-drag car (tubbed, no-shock towers) that I'm converting to an "open track" car to run local shelby events. Sears Point is my home track (ten minutes away) but I'd love to go to Willow Springs (and T. Hill & LS) when the car is complete.

Does any of this method of preparing the car for smog apply to a 400E?

All Merc engines with the KE systems have the same emission control technology, and analysis of test numbers and troubelshooting are basically the same. The one fly in the ointment are those models with air pumps. If they are set up to only inject air during cold mode, then analysis of the emission numbers is that same as what has been discussed here.

If they inject air all the time - including normal warmed up operation, the O2 content in the exhaust cannot be used to analyse converter efficiency. My car predates the adding of air pumps, so I'm not sure what modes they are active, but maybe someone else can chime in.

Three way catalysts work best with the native exhaust consituency that occurs with a stoichiometric air fuel ratio, which has a faction of a percent of oxygen, so air pumps on modern cars usually only inject air to reduce CO and HC during warmup. Once the O2 sensor heats up enough to allow closed loop operation supplemental air injection is suspended, and for this reason, many air pumps on modern cars are electically driven rather than engine driven.

Duke

Hi John

Looks like you are almost there.

Your new numbers indicate a marginal improvement which would indicate to me that the "Cause" has yet to be addressed.


I am curious about the following items: 1) How is the "idle quality" on your car? 2) Have you had the "CO adjusted" yet? 3) Have you installed a new "O2 Sensor?" 4) Did you install an "OE cat?" 5) If “No” did the replacement Cat come with "Pre-Cats?" 6) Have you replaced the distributor cap and rotor in the last two years? 7) And is your “intake system” sealed well? (IE: injector seals, pcv hoses, idle valve hoses, and rubber boot under the fuel mixture housing)

Over time subtle intake leaks do develop in these areas which become masked by adjusting the CO, at some point the engine is simply too “Rich.”

Good Luck!

Hey Mr. CJ

To answer quour q's:

1) Idle quality is better than most 300e's, but like all that I've seen idle is better when the motor is cold.

2) CO will be done this week

3) Ne O2 senson two year ago

4) Aftermarket cat

5) Pre-cats are orig to the car

6) Cap/rotor/wires one year ago

7) Intake test for leaks - passed


Let me know if I'm missing anything and thanks for your input!

Duke,
excellent diagnosis,
I too work with emissions, we have the latest & greatest IM 240, results are in mass, grams pollutant/miles driven. A passing standard for an 86 would be .8 grams per mile of HC. So do the math and see how much even clean cars emit in a 20K mile year, multiple that by 1.3 million cars that are OUR test area alone, one city in one state, then muliple that by a factor of 4-700 and one gets a general idea of why cars are targeted for reducing emissions.
its all in the numbers.

Tangas,
Beautiful numbers. Obviously good maintenance and attention to the vehicle.

Manny,
CARB RULES!...(and regs) so does CDEQ!

If your CO mixture is set to factory specifications (40% to 50% using factory test device) and you discover the CO is still elevated than the Pre-cats might be the cause.

My personal preference for Mercedes vehicles is to always lean in the direction of a factory catalytic converter. Good, bad, or indifferent it simply is a personal choice.

Do you know if the air pumps on later 103 engines inject air all the time or just during warmup? If the latter, how is it controlled? Is there an electromagnetic clutch on the pump pulley?

I don't work in automotive emissions now, but I did graduate research in the field at the University of Wisconsin Engine Research Center.

Duke

Same question. How is the air pump controlled to only inject air during warmup.

If the air pump operated all the time the exhaust consituency into the converter would not be correct for NOx reduction. That's why air pumps on modern cars usually only inject air during warmup.

If the pump control system was modified to inject air all the time, it could reduce high CO or HC, but NOx could be a problem. If CO or HC is high the fundamental cause of the problem should be corrected rather than trying a band-aid solution.

Duke

Just during warmup, it's function is to assist with heating the catalytic converter. Much like building a fire, if you blow on the coals they get hotter due to the increase in oxygen.

Same concept.

Duke,

There is a thermo-vacuum switch, which either opens or closes (can't remember right now) when the temp comes up. The vacuum line comes off that swicth to the right fenderwell(might be different for a 300E) where it attaches to the power switch for the AIR pump.

So you're saying that the pump continues to pump air, but a switching valve diverts the air and dumps it overboard rather than injecting into the exhaust once the O2 sensor is hot enough to enable closed loop operation(?).

Duke

Yes about the EM clutch,much as others have said, the AP works for about 110 seconds or until temp is around 110*F(40*C) and RPM is less than 3000,and is in closed loop. The EM clutch is switched on by the CIS-E control, which is controlled by the MAS control unit. The MAS unit at the same time powers up the change over valve which gives vacuum to the air shut-off valve in the pump circuit, air is then pumped into the exhaust ports of the cylinder head to aid in combustion of those HC's and heat the cat up. But contrary to ones opinion of excess drag on the engine, the EM clutch eliminates any drag to a neglible amount.

Doers the O2 sensor fail gradually?
 

I passed the TX smog test but not by much. I will post the numbers if needed. My 87 300E has 320K miles and has not had the O2 sensor replaced in the last 200K miles at least. Can it be bad even if the car runs ok?

I'd like to see your numbers, and the passing limits. (I'll give you a free analysis.) Also, what kind of test? List CO2 and 02 if available.

Most cars will run okay with a bad 02 sensor. On board diagnostics will pick up some failure modes, but not all. 02 sensors can get "lazy" with age and respond slowly, which can effect emissions. Modern OBDII systems might be able to pick this up, but not your vintage electronics.

You can eavsdrop on the O2 sensor with a scope and make a subjective analysis of its behavior.

Duke

Here's another recent KE emission test data set from a '88 560SEL owned by a friend. Car is well maintained with 160K miles. O2 sensors, cap, rotor, spark plug wires and valve seals have been replaced, but no other major work has been done to the engine or fuel system and the converters are original.


15 MPH (1438 RPM)
CO2 15.0%
O2 0.0%
HC 70/100/31ppm
CO .06/.67/.10%
NOx 39/741/237ppm

25 MPH (1452 RPM)
CO2 15.0%
O2 0.0%
HC 42/74/20ppm
CO .05/.54/.09%
NOX 38/680/199ppm

Note that O2 is zero so the converters are operating at 100 percent oxidation efficiency, but the HC is still about double the average for this year group. Also, NOx is commedably low, so the converters must be reducing very efficiently.

These numbers are roughly comparable to Mike Tangas' 560 numbers posted earlier. I attribute the difference in CO2 to different fuel blends with a slightly different carbon to hydrogen ratio.

Duke

Duke

Well, the car finally passed smog but not by much. My mech fooled around with it for an hour on Sat. and I watched. What seems to help the most was a hot cat.

If you recall, I replaced the cat but not the pre-cats. The odd thing now, at least to me after reading all the posts here, is that my O2 went from 0.00% with the old cat to 0.04% with the new.


Anyway, here are my numbers:

initial / last / max:

15 MPH

CO2 13.50 / 14.47 / NA
O2 0.00 / 0.04 / NA
HC 187 / 122 / 126
CO 1.67 / 0.64 / 0.79
NO 460 / 250 / 1316


25 MPH

CO2 13.70 / 14.60 / NA
O2 0.00 / 0.03 / NA
HC 166 / 77 / 101
CO 1.31 / 0.47 / 0.59
NO 417 / 239 / 1112


As you can see, the car is cleaner at a total cost of about $600 which included oil change, plugs, cat, an hour of mech time, and several attempts on the smog dyno. The car now has a two repreive until the nest smog. It will then likely become a doner vehicle or my permanent mexico ride at a friends home in cabo. Thanks to all who responded!!!!!

Typical KE test results - high or barely passing HC at 15 MPH. The 25 MPH HC is better due to converter heating during the 15 MPH test.

This is the first CA ASM test where I have seen O2 measured to the hundreth of a percent as apposed to tenth of a percent. Can you confirm this?

Assuming your first test yielded accurate results there was no O2 and high CO because your mixture was way rich - outside the range where the O2 sensor and electronics could correct it to stoichiometric assuming the O2 sensor and electronics including EHA were functioning properly.

My suspicion was that your converters were okay, but the mixture needed checking by observing the duty cycle and then going from there to correct a rich mixture condition. A hotter converter should also reduce more NOx creating more O2 for oxidation. Your NOx numbers are fairly low, but every little bit of additional reduction helps when your HC is at the ragged edge. You're CO is close to the limit indicating that the mixture is still marginally rich.


If you still have the car up here in two years have it tested on a rainy day (if possible) and ask the tech to run the "tire dry test" - no load at about 2000 RPM for a minute. This will heat a converters a bit and hopefully provide a passing margin on HC at 15 MPH. The few hundreths of a percent O2 indicates that the HC could come down a few ppm if the converters were 100 percent efficient on oxidation to get the O2 number down to zero, and the hotter the converter, the more likely the probability that all the O2 will be consumed by oxidizing HC and CO.

Duke

O2
 

Duke

Thanks for the follow-up!

Yes, the O2 is measured down to hundreths. I be happy to fax the before and after results to you.

Duke here are my numbers for my 87 300E
 

25 mph- RPM 1671 15 mph-RPM 1737
HC in PPM 76 (148 is standard) 149 (152)
CO % .17 (.94) .3 (.8)
CO2 % 15.1 15
O2 % 0.1 .2
NOx 621 (1047) 1073 (1146)
dilution 15.3 (>6) >6


last year's results

HC 34 87
CO .2 .4 (.86)
CO2 14.6 14.4
O2 13.8 these are the numbers 12.8
NOx 611 1107
dilution 14.8 14.8

2001 year

high speed RPM 2650 low speed RPM 693
HC 21 36
CO .18 (1.2) .02 (1.2)
CO2 14.9 13.2
dil 15.1 13.2

Thanks for any comments

What kind of test was this - I/M 240? Our CA ASM test is a bit different, but I'm not familiar with I/M 240 at a low level of detail.

Also, what is "dilution"?

Your results are similar to what I see with 103s on the CA ASM test - barely squeak by or marginally fail on HC on the first test (15 MPH), better at 25 MPH when the converter is hotter. Since you had 0.2% O2 on the first test, a hotter converter at the start of the test probably would have reduced HC and given you a little more margin.

Your CO numbers indicate that the mixture is probably okay, so the O2 sensor, electronics and EHA are working.

In the last several years that we have been subjected to ASM testing in CA the NOx measurements and standards are all over the place, and I can make not sense of them from test to test. I can only conclude that the CARB who controls the test software is still trying to figure out how to accurately measure NOx. Most recent tests indicate lots of margin against the limit, but yours is close to the limit. I can't offer any constructive comments on the NOx numbers.

The degradation from the last year's test could be due to a colder converter, or degradation of the converter. They do degrade with use, but should last well over 100-200K miles if oil consumption is not excessive.

The key is to have the converter as hot as possible prior to the test. Run it at 2000 revs with the A/C on defrost prior to the test. Go to a drivethrough place where you wait in line - like a car wash. Pick a day when the line is short or you can get right in.

Duke

more info Duke
 

the TX test calls itself ASM version 0305.
Dilution is given in % at the bottom of the page and I do not know more except the test wants it to be >6%.
My cat has 320K miles on it. I checked O2 sensor has 320K miles also.

thus my O2 sensor must be ok if the CO is low-true? If so I will not change it at the next tech session.
Thanks.

Wow! 320K miles on both the catalysts and O2 sensor. Yes, from the CO reading the O2 sensor appears to be okay. Just make sure everything is hot as possible for your next test.

Duke

I just barely passed the smog test. I'd appreciate commentary on the following numbers, as I'd like to make sure that I implement all of the necessary adjustments so next time it is not so close.

15 MPH

measured (max)

RPM 1525
%CO2 15.5
%02 0.9
HC(PPM) 110 (110)
%CO 0.28 (.71)
NO (PPM) 676 (850)


25 MPH

measured (max)

RPM 1479
%CO2 15.0
%02 0.8
HC(PPM) 53 (85)
%CO 0.13 (.59)
NO (PPM) 271 (783)


Thanks in advance.

Steven

As is typical for 103 engines you are on the ragged edge of HC at 15 MPH. The 25 MPH numbers are always better because the converter heats up during the 15 MPH test. Given the relatively high level of oxygen there is definitely room for improvement to reduce both HC and CO, and the hotter the converter the better it will oxidize HC and CO.

Frankly, with the level of O2 you have I'm surprised it passed. It's common to be at or near the HC limit with a tenth or two percent of O2. The fact that you have relatively high O2 and reasonably low CO indicates a good mixture, and no adjustments are necessary. For your next test make sure the converter is as hot as possible.

Always drive the car for at least 15-20 minutes before the test, preferably with a freeway run. Go to a "drive through" test establishment at a time when there is no line so you can get right in. Prior to turning the car over to the tech, keep the engine running at 2000 revs in neutral with the defroster on so the A/C compressor puts some load on the engine.

If possible, go on a rainy day and ask them to run the "tire dry procedure". They will run the car on the rollers with no load at 2000 RPM for about a minute, and this will heat up the converters.

The 103 engines are typically near the limit, especially at 15 MPH, even in perfect adjustment and operating order, so you have to "manage" the test procedure to ensure that the converter is as hot as possible when the test begins.

Duke

Thanks very much Duke. I'm happy to hear my mixture does not need further adjustment, as I just finished modifying my lambda settings a week before the test, and I wasn't completely sure how well my mixture adjustment would work out.