1989 W126 300SE Passed Emissions Test
 

By that much.

The 15 mph test was fine. The 25 mph test wasn't so good.

Test_______limit__ reading
HC ppm____ 103__ 54
CO% ______ 0.63_ 0.22
NO ppm____ 729__ 727

Looks like I have some vacuum leaks
I'm going to fix them so the reading is lower.

What makes you think that you have vacuum leaks?
The high NOx would normally be caused by a suspect/defective EGR system.
Your HC & CO readings are very good.
Often, vacuum leaks are accompanied by elevated HC readings. ;)

My 300SE doesn't have an EGR. I figured vacuum leaks because the rubber bits look like the original ones and are hard and one is cracked near the end of it.

nox
 

High nox can be caused by a clogged or malfunctioning catalytic converter. But before I assumed that, I would drive down the tank to empty, put diesel fuel injector cleaner in there, drive the car hard until about 1/8th a tank is left then go test again while the car is hot. A dirty intake system can cause high nox, I have seen it and also read it (a reason why so many injection cleaners claim they help emissions, they can). You may have a vacuum leak anyway. But if that were causing this problem I would expect to see the other readings off more especially if the car fuel/air were manually adjusted to work around the vacuum leak to improve idle. But these are sensitive systems so who knows what anomaly can occur in al circumstances.

Also using a grade of fuel other than supreme in that model can increase NOX by more rapid burning. The jury is still out, but someone posted here a few months ago about failing NOX as a gross polluter until he changed his radiator. I want to test that theory, but the 88 and 90 300SELs I have been fighting with have been failing in the HC category.

Peter

The rate of flame propagation does not vary significantly between gasolines with different octane ratings as long as there is no detonation, and the same applies to peak temperature of the flame front, which is where NOx forms. "Premium gas burns slower" is a myth!

To the thread originator - I don't think there is a "problem" with your converters, but it will help in diagnosis if you would post the entire test results for both 15 and 25 MPH including the 02 content.

Duke

If fuel grade doesn't make a difference,then there a whole lot of us out here that have misinformed by articles in professional journals, the mfgs of the testing machines, and I believe the State of California, but don't quote me on the last, because I have to check my references.


Peter

Make a difference regarding...?

The "premium fuel burns faster" myth probably originates from not understanding the nuances of combustion and the difference between normal and abnormal combustion.

If you use fuel with insufficient octane in an engine and it detonates then, yes,combustion is "faster" because detonation is virtually instantaneous, but this is ABNORMAL combustion, and most engines will not survive long under continuous detonation, so the point is somewhat mute.

If you use a higher octane than the engine needs, there is no signficant difference in normal combustion flame propagation rate, and there would be no statistically signficant difference in emissions. If the octane rating is too low and the engine detonates, then it's a whole other ballgame.

Duke

We may be talking about 2 different things here. :confused:
Fuel " grade ", i.e. octane rating, vs. Fuel composition, i.e. oxygenated, ethanol-blended, etc.
In which case I believe there to be a slight difference in exhaust emissions.

The idea of oxygenated fuel was to provide more O2 to help oxidize CO and HC on pre-O2 sensor cars, which are getting pretty rare nowadays! It should also function the same way on an O2 sensor car during warmup prior to going into closed loop operation, however, evidence indicates that oxygenated fuels do little to reduce emissions, but they are more expensive to produce and increase fuel consumption about three percent because they have less energy. Their cost far outweighs their benefits in even the most "liberal" economic analyses.

In closed loop operation an O2 sensor engine will just richen the mixture slightly to maintain the target near zero 02 reading in the exhaust.

The Schwarzenegger administration has actually petitioned the EPA to eliminate the oxygen requirement for California gasoline. The EPA is the source of the requirement, and it's more about placating the farm lobby than clean air.

Duke

OK, I'll post the results from the 15 and 25 mph tests in the morning.

The 15 mph test at 1504 rpm, dilution 15.6.

Test _______Limit_____Reading
HC ppm_____106______29
CO%_______0.59______0.10
NO ppm_____800______312


The 25 mph test at 1527 rpm, dilution 15.8.

Test_______limit______reading
HC ppm____ 103_____ 54
CO% ______ 0.63____ 0.22
NO ppm____ 729_____ 727

I don't know what dilution is but I added it here.

The car is also OBD-I so there's not much more available. I would like to upgrade to OBD-II and EFI for better performance. That would cost a lot of money though.

Before I comment, I'd like to see the O2 content. This looks like the California developed acceleration simulation mode (ASM) test, and our reports list the O2 content, which is an important diagnostic tool.

Also, what is the odometer reading?

I don't know what is meant by "dilution". It might be defined on your test report. The web site for your state agency that administers the emission test program will probably have a definition and more information on how to iinterpret the report.

Duke

There is no O2 reading on the test. From the Va. Dept of Environmental Quality, here is the definition of:

Dilution- This is a measurement of carbon monoxide and carbon dioxide in the exhaust stream. If the vehicle being tested is determined to have "invalid dilution," that could mean that the vehicle has an exhaust system leak, or some other problem that prevents a valid sample of exhaust emissions that must be repaired in order to be properly tested for emissions.

Odo reading 156032 miles, 6 cyl as well, M103, OBD-1.

http://www.deq.virginia.gov/mobile/mobfail.html

http://www.deq.virginia.gov/mobile/homepage.html

Your test results are different than the typical M103 readings in CA. M103s tend to be high on HC - close to or a little above the limit - on the 15 MPH test, but much lower relative to the limit on the 25 MPH test. I attribute this to the converter being relatively cold at the start of the 15 MPH test, which is why "conditioning" is important i.e., go to a drivethrough test station with a short line with the car thoroughly warmed up (at least 20 minute since the cold start) and keep the revs at 2000 with A/C or defroster on, so the compressor is placing load on the engine.

The 15 MPH test has a relatively higher load than the 25 MPH test and heats up the converter. The O2 content indicates how efficiently the converter is operating. If O2 content is zero, then the converter is operating at max oxidation efficiency - using all the available O2. Typically the O2 reading is a little higher at 15 MPH than 25, indicating that converter efficiency is higher on the second test, which is the 25 MPH test. O2 content is typically zero to 0.3 percent and anything above zero means that HC can be reduced if the converter is hotter.

The higher NOx in the 25 MPH test is inexplicable to me given that this test is done at lower relative load, and you can see that the stardard is a little lower than at 15 MPH. Given that your 15 MPH NOx is well below standard I cannot explain the high number at 25 MPH, but I would not discount test or measurment error. I've seen this before.

For example, my '91 MR2 was tested last year and the O2 content was 2 percent with passing scores on the pollutants that were well below standard. Such a high O2 reading on a O2 sensor car is virtually impossible unless there is a malfunction and none iwas indicated either by the OBD or test results. Prior test showed zero to 0.1 percent O2 with very low emissions.

Keep you test report and if you have previous test reports keep them all together or handy so you can look at trends, which are useful in diagnosing emission problems.

P.S. Ignition timing has a signficant impact on emissions. The M103 ignition system controls advance based on a combination of engine speed and load. Load is represented by manifold vacuum - higher vacuum is less load, and usually more advance via the vacuum advance system. Retarding the timing from normal will reduce peak flame front temperature, which reduces NOx generation and increases EGT, which will get the converter hotter, faster and reduce HC and CO.

One "trick" you can use if your M103 is on the ragged edge or marginally fails is to disable the vacuum advance by plugging the vacuum line to the EZL module. Also, there is a resistor module plugged into a pigtail and the value affects the rate of advance with engine revs. There have been a number of discussions on this and IIRC it you short the plug (zero resistance), the rate of ignition advance will be slower, which will retard the timing for any speed load condition relative to the OE timing map.

Since the 25 MPH test is done at lower relative load, there would probably be more ignition advance due to the vacuum advance.

The fact that engine revs are the same indicates that the 15 MPH test was second gear and the 25 MPH test was in thrid. Some ignition advance systems also use transmission gear to determine advance, sometimes by locking out vacuum advance in the lower gears. I don't know if this is the case with the M103.

Duke

your readings
 

are excellent for the car, don't overanalyze it. Your Co and HC are very good. Run some diesel fuel injector cleaner in there as I suggested and see how it goes. The state of Virginia has actually made it harder on these cars, if you go back to your tests 2 and 4 years ago you'll probably see the NOX limit has been lowered meaning the car must perform better.

High NOX is not 700 or so. It may be for the state of virginia but isn't for an older car. I've been amazed by my own propensity, and that of many folks, to react to a number that is at or slightly above a state limit. The state limits are somewhat arbitrary and do not take into account age of the car, age of the catalytic converter, etc. I've studied the equations, relationships, etc between NoX, oxygen, etc etc etc. I can tell you that you are on the path to hell here if you overdo it-- I did that. If you sense the car is UNDERpowered then you have a reason to go in there and determine if the cat is clogged, etc. Of course check for vacuum leaks but I don't see that as a likely cause here per my other post, but what do any of us know really in the end since we guess with an esoteric thing like NOX value.

If you are experiencing less power with the car, then you probably have a clogged cat. I don't know if your car has pre-cats, but they can clog. If your power is good and everything else is good, run some cleaner in there and leave it alone. Trust me, you're on the way to a very big litany of stuff that may result in a better car in the end (maybe more power) but great expense as every mechanic or you go in there and try to guess the thing out. If it really bothers you, other than cheap and easy things you can do, the other thing is to put a Miller cat AND pre-cats on there costing you $1200 to $1500 for someone else to do it or I think about $600 parts plus whatever labor you can find-- that's a quote for another MB (mine).

Thanks for the comments.

I had driven the car from work to the testing station, I work at night, for a distance of approx. 35 miles. The car was operating at it's normal temperature of 87C. I told the inspector this and he let it idle for a while anyway. I've dealt with this inspector before and he knows I work on my cars. I'm always up front about what I've done mechanically to the cars. The inspection stations in Va. perform mechanical and smog testing.

I suspect the rubber hoses have hardened and need to be replaced. The plugs, wires and cap need to be replaced. There are many little hoses which also need to be replaced because I suspect they are mostly original. I'll also get a generic O2 sensor and replace it.

When the car is cold and the air temp is around 50F, there is a low speed lean condition or stumble. When the air temp is less than 40F, it runs well. I suspect a temp sensor or vacuum switch. The injector seals may also be bad. I think the PO's did minimal maintenance on the car based on some of the things I've seen. I also have to replace the serp belt pulleys because they are making some noises.

The car is really nice but it's a money pit.

I don't want to hijack the thread, but your comments got my attention. Some time ago, I had classes in college that were tought by the same prof: thermo and internal combustion engines. I remember considerable time spent on flame front propogation, heat transfer, etc. It was stated emphatically that octane is designed to "provide a slower flame front" to maximize power output and minimize detonation. Too low octane in some engines, usually higher compression and timing design, will assure detonation. It can get so hot in some engines that you can get autogenous ignition - same as diesel - when the piston is compressing the fuel/air in the cylinder. It's been a few years since those classes, but I'm guessing the Laws of Thermo have not been thrown out. ;)

Also, here is some written info:
______________________________________________________
This is not meant as a challenge to you, rather asking for more information or explanation.

Duke,
I won't get into the required octane bit right now, because I don't have time to dig up, scan, and post the documentation. I wouldlike to discuss changing timing on the M103. I don't understand what you are talking about with vacuum advance. :confused: The distributer is bolted to the front of the cam with no advance capability. Your thoughts on replacing the resistor that maps the EZL are interesting. I'll have to experiment with that. I got rid of my 90 300SEL, which was a bear to pass smog, but, I still have an 88 300SEL. The 88 has a problm just getting by on the 15mph and 25mph HC readings and my O2 is .5 %. I'm trying to figure out why some M103s fly through the test and others get bogged down in the HC category. NOX has never been a problem. About plugging the vacuum line to the EZL, you might get away with that on most year Federal cars, because the only thing that will trigger the MIL in Federal cars is the oxygen sensor. Not so with California cars, because you will trigger a code 16 and set the MIL. TRhis is also applicable to the M104 engines.

Warren,
If you are hearing sounds from places like the fan pulley, the bearings are probably about to grenade on you. As too your stumble, Folks in other threads have been very successful in curing cold idle problems by tweaking the screw on the back of the EHA. I haven't had a chance to experiment yet.

You have a luxurious $3000 car that still gets attention, costs you several hundred dollars, and you call it a money pit. Buy something like a new 04 Dodge Neon if you want to own a money pit. Yes, you have to keep putting money into that old car, but save your receipts for 5 years. Acturial tables show that the $13,000 Neon will cost you over $30,000 in the first 5 years of ownership. Many years ago a friend got a job that required a 60 mile or so commute for about a year. He started a car pool with 3 other guys. They all went out and bought new little economical rice burners. My friend bought a 65 Pontiac Bonneville for $500. They always wanted to use his car, because of the room and A/c, but they all shared as per the agreement. Afret the year was up, they had car payments, registration, maintenance, and insurance on cars they didn/t need. My friend sold his Pontiac to a low rider for $500. He had cheap registration, basic insurance, and a few hundred extra dollars in fuel costs.

Peter

Regarding the flame front propagation issue, note that I said that in the ABSENCE or DETONATION there is no significant difference in flame front speed and your information does not dispute this. Detonation is "abnormal combustion" and is a whole other ball game than normal combustion, which is detonation free. If you can use regular unleaded without signficant detonation as I can in my 2.6, then there is no difference in normal combustion flame front propagation speed. You have to differentiate between normal (no detonation) and abnormal (detonation) combustion. Generalities such as "premium gas burns slower" does not capture this critical distinction!

If your engine detonates consistently on a given fuel octane, you better increase the octane in short order before you cause permanent damage. Brief transient detonatation, such as what might occur if you short shift, will not cause any harm, and can usually be avoided by changing your driving habits - like shifting at higher revs and easing into the throttle.

On the vacuum advance issue. I have not actually tried to block the vacuum line to my EZL module, but I will probably try it when I bring the 2.6 out of summer storage for use this winter. It's due for an emission test in February. It appears that the vacuum line to the EZL is an input to igntion timing. Why else would it be there? I'll report on the results of my experiments and my emission test results.

Like your M103s, mine is on the ragged edge of the HC limit at 15 MPH. My theory is that the catayst bed cools off after several minutes of idling, which reduces oxidation efficiency, and this shows up as high HC and (relatively) high 02 on the 15 MPH test. The load during this test causes the converter to heat up and the HC and O2 go down due to higher catalyst oxidation efficiency; 0.5 percent O2 is very high and inidicates poor catalyst performance - probably due to low temperature. Good converter action should result in no more than 0.1, maybe 0.2 percent, O2. If the O2 level is zero, the converter is operating at "100 percent efficiency" using all the available O2, and at this point no further reduction in measured emissions is possible. My other theory is that 02 sensors may "drift" in their calibration, but I have not been able to confirm this. Reports I have read indicate that O2 sensor degradation results in increased response time, but this too could cause higher emissions.

If you have an IR gun run the following experiement. After 20 minutes of normal driving check the converter inlet temperature with the IR gun. Then let the engine idle and check temp. every minute. It will probably go down significantly within five minutes, which would indicate that the catalyst bed is also seeing a signficant reduction in temperature, which will reduce its oxidation efficiency and increase HC and CO.

Duke

Reason for hi NOx maybe
 

It well could be the passaged for exhaust gas recirculation are partially or nearly completely closed off(plugged). Not uncommon, particularly on higher mileage cars. Some shops even clean them out every 30K service. Easy to use a 'spedometer cable' as a snake drill in a variable speed drill, and dribble carb cleaner down the spinning cable as you feed it in.

Thanks Peter.

I bought the car a year ago for $5K and I knew it was going to need some work. I've overhauled most of the front suspension but I'm going to have to do more. I have a used PS gear to install because the current one is loose and knocking (not the mount). I also have a replacement rear window to install.

I'm convinced that used cars are the way to go, let someone else take the hit on depreciation. I can fix cars and I don't mind. I get to drive a fabulous car and people do look at it.

I'm going to try tweaking the EHA as you suggest.