Failed Emission Test - 1989 420SEL
 

My 1989 420 SEL with 255,000 KM failed the provincial emission test. There is long list of what could be the problem. Here are the ASM tailpipe emission inspection results:

ASM 2525
HC PPM limit:50, reading:101, result:fail
CO% limit .28 reading:.18 result:pass
NO ppm Limit:548, reading:241, result:pass
RPM 1414 result:valid
Dilution: 15.6, result valid

Curb idle
HC PPM limit:200, reading:72, result:pass
CO% limit 1.00 reading:.08 result:pass
NO ppm Limit:N/A, reading:N/A, result:N/A,
RPM 665 result:valid
Dilution: 15.0, result valid

Engine coolant temp 85c.

I was told the high HC during driving test or high idle causes could be:

vacuum leak
ignition system malfunction
faulty computerized engine management system and or oxygen sensor
faulty air injection system
internal engine problem
failed catalytic converter

In November 2005, I had a valve job done, new intake manifold o-rings, new chain and guides, new plugs, air filter, new head bolts, mercedes gaskets, oil change was about 1,000 KM ago, using 5w50 synthetic. o2 sensor is about 3 years old. Prior to valve job, had a rough idle. Mechanic who did valve job said definately part of the rough idle job problem was the 0-rings, they were hard`as rock, also said the my ezl was OK.

The car runs great!

Any ideas?

If your system is working properly in closed loop, I'd guess the catalyst is dying or was cold.

50 PPM is an awfully tight limit for ASM 2525. What has this limit been in the past?

I have recent California ASM results for a buddy's '87 560 SEL and it scored 42/74 on the 2525 test. In CA the 2525 test is preceeded by the 1550 test, which is the tough one. Dave's 560 was 70/100 and the best mine has been in recent tests is 73/116 on the 1550 and 47/91 on 2525. The 2525 is usually not a problem because the catalyst heats up during the 1550 test, which is the acid test if the catalyst isn't hot enough. There is no idle test in CA, but a move is on to add it.

Your limit would probably fail most KE-equipped Mercs in California as few can score much under 50.

I assume your test is only 2525 and idle? You didn't report the O2 level. Is it listed on your test report?

There's appears to be a move to tightening limits in many jurisdictions to the point where more and more cars fail.

Suggest you look at this thread and the others it links to:

http://www.peachparts.com/shopforum/showthread.php?p=833484#post833484


I don't think there's really anything wrong with your car. If the O2 is zero, the HC can't get much lower. Relatively high HC is the nature of the KE-beast, which is why "conditioning" is so important. Old cats need to be REAL HOT!

You may want to take the limit issue up with your emission test authorities.

Duke

I'll say it for the 1 000 000 time , MONEYGRAB !!!:mad:
Take all the C.A.R.B guys out back & shoot them ( ignorant S.O.B.s...everyone I've ever met). :rolleyes:

Update
 

I do not have anymore readings from the inspection, everything was posted on first post. Yes, only the ASM2525 and the curb idle test, plus the gas cap pressure test are conducted. Apparently the limits were lowered in 2005.

The car was runnning for about 45 min. with a 15 min. highway run at 100 KPH but then it sat in for 50 min. in -5c temperature. The testor was 30 min. late. I actually went out and started the car about 5 min. before the test and got the coolant temp. backup to about 85c as the guy came out to get the car.

When you say catalyst, is that the catalytic converter? and is that the part of the exhaust system, connected to the crossover pipe, where the o2 sensor is?

The HC ppm reading is double the limit. How can I get the cat. hotter and what is the probability that it will be cut in half just becuase of heat, to less than 50 from 101?

I do have a brand new complete exhaust system from timevalve, hanging on the garage wall. The existing exhaust is still in decent shape.

Should I just replace the exhaust system? Should I go for a diagnostic to determine the reason for not meeting the emission standards? If I go for a diag., should I go to the dealer or any certified repair tech. shop, like the one that did the test?

The emission report does state a repair cost limit of $450. I can get a conditional pass, if I spend at least $450 on emission related repairs (including parts, labour , diagnostics). The car cannot be sold with a conditional pass but I can get the plates renewed.

Yes, catalyst and catalytic converter are the same thing. They are the first "units" after the 02 sensor, and your engine might also have "pre-cats" just aft of the exhaust manifold.

If you read my referenced posts you should understand that lack of proper "conditioning" is an absolute recipe for FAILURE.

You must arrange that the car is tested immediately after a good warmup that includes high speed driving and brisk acceleration, and NEVER, EVER shut down the engine prior to the test. You have to "manage" your test.

Letting the car sit for 50 minutes in sub-freezing temperatures is just not going to cut it, and idling the engine to warm the coolant will not get the catalysts hot enough.

You're probably going to need to retard the timing by shorting the R16/1 resistor and disabling the vacuum advance as I discussed in the other threads.

This is a lot easier and certainly cheaper than replacing the catalysts, which won't in and of itself gurantee a pass.

Duke

Prior to 2005
 

The HC ppm limit was 58 prior to 2005 in the province of Ontario, for the ASM 2525 test. In 2005 it was lowered 50. Last time the car was tested the result was 53.

So I am hearing that I should go for a retest as soon as possible and make sure to rev. the engine for at least 10 min. at 1500 to 2000 rpm until the technician arrives to take the beast into the test. The re-test is only $20.

The last time I checked, Mercedes list for the cat was C$2,200. I hope the timevalve cat. lives up to spec.

Where is the R16/1 resister located? How do I disable the vacuum advance?

Yes you hear correctly.

I don't know where the R16/1 resistor is located on your model. Maybe someone with a 126 can help out. Remove the resistor and replace it with a home made shorting plug - like a short piece of 12-gage wire with the exposed ends folded over so they make good contact with the pin receptables.

On my car there is a short piece of rubber tubing that connects from the manifold port to the nylon line that routes to the EZL module. This can be replaced with a piece of 1/8" vacuum hose with a slug of silicone sealer that is allowed to set up.

With these temporary mods, the car will feel VERY sluggish at low revs, but the retarded timing will considerably increase EGT, which will help keep the converter hot. The substitute parts can be removed and replaced with the OE parts when you are done with the test. Once you know the drill it only take of couple of minutes to configure and de-configure for emission testing.

Duke

Question for Duke 2.6...
 

Hi there,
I have a question for you - I read on another site that running on about 50% alcohol will greatly reduce the HC emissions. What is your take on this - does it screw up some other part of the test, and is it observable to the tester?
I always retard the timing slightly and add a gallon of alcohol to a quarter tank of gas before going in, and have good results.:)

Alcohol adds oxygen to the fuel. In CA we have about 2 percent oxygen by mass (about 10 percent ethanol by volume) in our gasoline year round. The "rationale" is that it reduces HC/CO during warmup (prior to the system going into closed loop when it runs slightly rich), but the reduction is marginal and even CA has asked the EPA for a waiver, but it's turned into another federal farm subsidy program, so no dice.

During closed loop operation the system just adds more fuel to consume the onboard O2. Oxgenated fuel costs more to produce and has about 2-3 percent less energy, so it reduces fuel economy by about the same amount for no meaningful improvement in emissions, but the farm lobby is strong and has Congress in their hip pocket.

Most HC failures (assuming the test report data indicates that the fuel system is properly functioning in closed loop mode) are due to the cat bed being too cold, which reduces oxidation reactions, and it's more of a problem as catalysts age and need to be hotter to achieve close to 100 percent of potential oxidation reactions than when they were new. Retarding the ignition advance map increases EGT and helps keep the cat bed(s) hot.

Fortunately our CA emission reports show O2 content in percent, and it's an excellent diagnosic tool. You want to see that number be 0.0. If it's 0.1 or more it means the catalyst is not hot enough to consume all the available O2 in oxidation reactions, but even with O2 readouts at 0.0 KE systems can read over 50 PPM HC on the loaded tests.

Bottom line is that adding alcohol to your fuel is of little value, and 50 percent alcohol will probably push the Lambda system beyond the limits of its control authority. What you need is a REAL HOT catalyst bed. Manage your emission control test so this is achieved.

Duke

Read up on the CIS/E system:

http://mb.braingears.com/126_DISC2/program/engine_420SEL.htm

Check out 07.3 and be aware that there is a potentiometer attached to the CIS throttle plate which goes bad. They are available and can be replaced but need to be properly calibrated.

You must also keep the car HOT as much as possible. Keep the car running while waiting for the test.

My last emission test also had high HC so I'm probably going to have problems next year, emissions are tested every two years in Virginia.

Foot + Floor
Loop Until Exhaust = Glowing OR T=2min.

Test Immediately :) hehe

A lot of people around here fail emission tests so I tell them to go get their car nice and hot before they go. They still fail and I have them demonstrate "conditioning" the car...and honestly it doesn't cut it :)

Let the beast under the hood come to life :)

Passed
 

I took the car into an "emission specialist" shop to get a diagnosis done. The guy quoted $60 to $120 for the diag., then whatever is wrong needs to be fixed, and then a retest is necessary. He asked me how much I was willing to spend,before he had to call me for authorization. I told him $200 is the limit. I called him 3 hours later, the car had passed, and the bill was $170 plus tax ($80 for diagnosis, $55 for combustion flush, $35 for emission test)

Here are the passed test results:

ASM 2525
HC PPM limit:50, reading:37, result:pass
CO% limit .28 reading:.14 result:pass
NO ppm Limit:548, reading:46, result:pass
RPM 1395 result:valid
Dilution: 15.0, result valid

Curb idle
HC PPM limit:200, reading:38, result:pass
CO% limit 1.00 reading:.08 result:pass
NO ppm Limit:N/A, reading:N/A, result:N/A,
RPM 661 result:valid
Dilution: 15.0, result valid

Very sweet! I am good to go for another 2 years.

If anybody in the Toronto area wants the shop name/address, private message me.

The diagnosis fee was a bribe to the cop that pulled him over while he was doing 120MPH performing the "combustion flush".

:D :D

What diagnostics did he perform and what was the result?

What's a "combustion flush"?

I take it you didn't witness any of this?

I could have probably gotten it to pass by just driving it around the block hard a couple of times and then running the test as quickly as possible

In CA we have a "tire dry test", which the tech can run on a wet day. As an experiment, I intentionally took my car in on a rainy day in January '01 and asked the tech to run the tire dry test, which is 30-60 seconds on the rollers with no load at about 25 MPH. He did this and then went right into the first test, which is 1550 and the HC was 87 ppm versus 121 two years prior against a limit of 141. O2 dropped from 0.4% to 0.0% so all the O2 was being used for oxidation by the catalyst. I attribute the reduction directly to the tire dry test which heated up the catalyst.

The HC limit for my car dropped to 116 in '03 and after barely making the cut at 113/.1% O2, my new knowledge about the ignition map got me down to 73/0.05 O2 in '05, and I don't see how it can get any lower.

Your first test was a marginal failure and was probably just a conditioning issue, but the car still has little margin.

You're probably going to have to go through this drill every time. Or you can work on your spark advance map and properly condition the car yourself, and probably pass on the first try, which is what this guy might have done given the substantial reduction in NOx, which was exactly the response from my engine, too.

Duke

I agree that those are some tight HC tolerances. For reference, here is the test conducted annually in Harris County Texas (Houston) that I had done last week. In the 6 years I've had the 300E, these are the lowest readings I've seen.

http://pauls-space.zftp.com/emissions.jpg

Those are very good numbers for a M103. The NOx leads me to believe that the timing map is retarded, but like most KE fuel system models, HC is high relative to the other emissions.

Does your engine have EGR?

I can't make any sense out of the O2 readings. Air has about 20 percent O2 and the exhaust gas should have near zero. In CA the O2 readings are given percent and an efficient catalyst will yield 0.0%. If it's more, like 0.1% or 0.2% the cat is not working at maximum efficiency, often because it is not hot enough.

One tenth of one percent is 1000 ppm, so even if the reading is 0.0 percent, there could still be enough O2 in the exhaust (a few hundred ppm) to promote more reaction if the catalyst is hotter, and this will reduce the HC number.

I wish the O2 readings were in ppm.

Duke

Info
 

HC is raw fuel. WHen you have to much air to fuel ratio, it can cause you to fail on the HydroCarbons. On newer mercedes and BMW's i've heard the Bosch Air Mass Meter has been a common culprit to high HC's, due to its premature death, but this is only what i've heard.

Below is the HydroCarbon break down from http://www.Aircare.ca they are the emissions company in BC. The company is under Translink control, however it is run by For Profit American company " ESP " under its Envirotest Canada division. In all ESP runs 80% of the emissions testing programs around the world. So all information you'll find under repairs on this site will directly relate to all emmisions programs.

-----
Possible Causes of High Hydrocarbon (HC) Emissions
Hydrocarbons relate to unburned fuel. You may logically think that must mean that the engine is getting too much fuel. However, that is only one of many possibilities ranging from fuel problems, to electrical problems, to internal engine problems such as piston rings that can cause HC emissions to be excessive.

In order to pinpoint the cause of excessive HC emissions, the following systems (if applicable) will need to be checked, usually in the order shown below:

Lean or Rich Air-Fuel Ratio
For an engine to operate as designed, the correct ratio of fuel to air must be delivered to the cylinders. If the fuel system is delivering a leaner than ideal air-fuel ratio, it may result in lean misfire and cause high hydrocarbons. If the fuel system is too rich, it also may result in high HC but will be accompanied by high CO as well.

For more info regarding the diagnosis of fuel delivery systems, see Fuel System Testing

Inadequate Catalytic Converter Efficiency
For vehicles that are 1988 model year or newer, it is very important that the catalytic converter be operating at 90% efficiency or better. That means that the emissions that come out of the tailpipe must be no more than 10% of what goes in.

For more info regarding how to determine catalytic converter efficiency, see Catalytic Converter Testing

Induction System Problems
There are many aspects of the engine's air induction system (hoses, intake runners, intake manifold, vacuum-controlled devices) that can cause disruption in the air and fuel getting to the cylinders and result in high HC. Incorrect PCV valve/orifice flow rate can also cause similar symptoms. Leaking EGR valves also may cause excessive HC emissions.

For more info regarding how induction system problems are identified, see Induction System Testing

Poor Ignition Performance
Ignition defects including dirty spark plugs, leaking or open-circuited spark plugs or wires, or defective ignition coils can all result in a shortage of spark energy. Any shortage of spark energy may cause high HC emissions.

If the spark occurs at the wrong time, incomplete combustion and high hydrocarbons may result. Too much spark advance could be due to an incorrect adjustment or a defect in mechanical or vacuum advance mechanisms.

For more info on testing ignition systems for inadequate spark energy or incorrect spark timing, see Ignition System Testing

Uneven Output Among the Engine's Cylinders
At this stage of the diagnosis the technician should be sure that the air-fuel ratio is correct, there are no external vacuum leaks, and the ignition system is operating normally. There are still many possible causes of high hydrocarbons, most of which are either internal engine problems or tough-to-detect induction system problems such as valve deposits or a leaking EGR valve. On fuel-injected vehicles, poor fuel atomization is a common cause of HC problems.

For all of these remaining possibilities, checking for uneven power output amongst cylinders will usually help to track down the cause of the problem. For more info on testing for uneven power output, see Engine Integrity Tests

-----

To Duke2.6
 

I do not know the details of the diagnostic. I left the car at the shop, and I was not present for the testing, etc.. I guess I could phone the shop and ask him about the "combustion flush".

I was so happy to see the "pass" report, I just wanted to get out of the shop real fast, to get my new license plate sticker.

am sure your specialist manipulated your emission settings for your car to pass the test - he did not fix the problem. it takes more than 200 bucks to fix emission related problems.

Joel you're so right. It cost's much more then 200 dollars. Also the Drive Clean program in Ontario is a private program run by certified shops using the ESP technology. Some of my family members have told me how they buy fraudulant tests in Ontario with their old beaters mostly used as work commuters. If their car fails, they go back to the shop towards the end of the day with a similar car that's in mint condition, weighs around the same and the mechanic punches the car in as the failure car...in exchange for a little payment under the table. Obiously the ghost car will pass fine, and your beater now has insurance. That's the main fraud i know lots people that are using in Ontario. Usually a proper emissions repair costs on average around 500-600.

In BC I know this guy in Port Coq., and if your mercedes fails the Emissions test, all he does is retards the timing for you and your set. For a little bit more money he'll put it on the scope and check the readings first and you're almost guarenteed to pass with his first adjustment. Go back and he changes it back to normal. I think in this case, this is what the mechanic did to this guys car, passed him, and charged him all this free money and laughing all the way to the bank.

p.s. Look to see if their's a hole in you're cat. Some mechanic's have this myth, that if you drill a small hole in the cat, it'll suck enough air in to dilute the readings. If you have to big of a hole, its going to say sample dilution and they won't be able to test you.

I, for one, and I think others would like to get an explanation.

Unless you get to the bottom of what happened you're probably going to have to go through this drill every time.

I'm very suspicious of what really happened. You should be too.

Duke

Duke, yes my M103 has EGR system. As far as the timing being retarded, I don't know ... I'm getting approx 19mpg in city/hwy driving.

Duke 2.6

F.W.I.W. here in Ontario ( where " Cigar Havana" is ), there is always a " Conditioning Mode ". This is a No-Load run for 2 minutes, before the actual test begins. ;)

Conditioning Mode for 2 minutes is interesing. ESP the designers of the testing software suggest that Conditioning beyond 1 minute is considered fraudulent testing. As this helps heat the cat up and you're beggining the test right away. Conditioning for 2 minutes and still failing...well then you know the car is hopeless and also its an inaccurate test in the customers favor. Drive clean seems to have its own issues...

Attached is a recent copy of Oregon DEQ test result for a 1992 300CE that I recently purchased. I have done nothing to this car. Carfax showed some failures to pass emissions and at one time labled the car a "gross polluter" in California, whatever that means. The car was run for 1/2 hour before testing and not turned off. It was NOT done on a dyno. The car passed but I think that the HC numbers were high and an wondering if this is normal????

118,000miles ; about 45 deg F outside temp

Oh, that's certainly worth something. In CA the only "conditioning" is the tire dry test if it's wet. Conditioning is a HUGE DEAL that the CA test authorities don't want to address. At lot of cars fail simply because of how they are conditioned, which is not uniform. There is no conditioning standard, and this makes it easier for unscrupulous operators to commit fraud by testing a clean car whose catalyst is too cold.

IMO all cars should be reasonably conditioned as part of the test so there's some basis for comparing results.

Our Mercs tend to be high on HC, and the limit keeps tightening even as the cars get older and should have more wear allowance. They can also be very low on CO and NOx. You can have very low CO and NOx, but if only 1 PPM above the HC limit, you FAIL. That's why I don't feel any guilt if I have to diddle my timing map a little to get more margin.

The government has run amuck. When are people going to stand up and say ENOUGH!?

Duke

A little knowledge is said to be dangerous. :rolleyes:

F.Y.I. ,I was instrumental in setting up the AirCare System in the Lower Mainland, back in 1988/89. ;)
I'm also familiar with the " Weak Points " of todays AirCare procedures.

It's not so much the government, as at is the Treehuggers. ;)
Never met one to this day that has ANY knowledge about cars, much less how automotive emissions are created.

When the government is driven on technology issues by people who don't understand technology, then the problem is the government. And in my experience, few in government who establish and enforce the various emission control/test programs understand the underlying science and technology.

Duke

Where did you do your test at?

I've noticed that some DEQ centers let you slide on a lot more (or their machines are far less sensitive?)....guy that works for a cab company selling/moving cars could NOT get a perfect vic to pass emissions in city of portland. Tried and tried and replaced tons of crap. Finally they took it down to sherwood DEQ test center and it flew with flying colors.

Interesting...


Newberg is DEQ excempt...though I would LOVE rolling in there with the diesel...haha

I took the car thru the DEQ center on Tualatin Sherwood Road. I work in King City and reallytried to get the CAT as hot as possible. I drove all over the back roads to Scholls, etc.

We've found (car guys around here) that the sherwood has often been the "easiest" to pass a car at...you might try a different place but I think that will be your best bet.

Doesn't help that you can't really keep the cat hot since Tualatin Sherwood road is hounded with fuzz regularly...not to mention traffic.

Hope you can figure out what is up...

REally... what kind of roll did you have? still work for them in any capacity?

Tree huggers think smart car's are enviro cars...haha, losers. They should be driving the now defunt electric GM cars, and always be 30 minutes late for everything.....

I second this statement!

Failed Again
 

My 1989 420SEL with 284,000 km failed the emission test here in Ontario.
ASM252 Test

At 1406 RPM, Dilution 15.3
HC ppm limit is 50 reading is 157 result failed
CO% limit is .28 reading is .34 result failed


Curb idle test,

RPM 665 dilution 15.3
HC ppm limit is 200 reading is 96 result passed
CO% limit is 1.00 reading is .10 result passed

Engine temperature was 85c. Prior to the test it was driven about 15 km, with speeds up to 80 kph for about 10 min.. Car stopped about 5 miniutes prior to the test.

Any recommendations?

Passed Again
 

Well she(1989 420SEL, 284K KM) is back on the road for another two years. I just squeaked through the test. I took her back to the emission specialist and $200 later, here are the results

ASM 2525

HC ppm: limit 50; reading 50; result pass
CO%: limit 0.28; reading .11; result pass
NO ppm: limit 548; reading 95; result pass
RPM: 1399 valid
Dilution 15.3 valid

Curb Idle

HC ppm: limit 200; reading 32; result pass
CO%: limit 1.0; reading .03; result pass
RPM: 806 valid
Dilution 15.2 valid

The guy told me next time I'll need a new catalytic converter.