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  #1  
Old 08-02-2004, 03:15 PM
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280 SEL Failed Emissions Test High NOX

My 1984 280 SEL Euro 110 six cyl failed the emissions test. Before the test I changed oil and air filter and filled up with 93 oct. the plugs are a few months old. The car passed emissions 2 years ago. The readings are:
HC 143.9 pass is 157
CO .10 pass is 1.00
NO 3312.3 pass is 1121.0
CO2 13.87 pass is ?

The NOX is about 3 times higher than passing.
The car has 185,000 mi and does use oil through the valve seals.
I searched for info and found that retarding timing and checking EGR valve may help but not sure if that will reduce the levels enough. Will a bad cat. converter cause these high levels? Any help will be appreciated.
Thanks, Bob

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  #2  
Old 08-02-2004, 04:26 PM
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How is NOx controlled on your engine? What were the numbers two years ago? Do you have any other prior data to review the NOx trend?

I assume that "Euro" model means it is a gray market car. Many of them were fraudulantly certified, so understanding the specefic NOx control system (if any) and the test history of the car will be important to correcting the problem. Given that you are three times the limit, I don't think that retarding the timing alone will get it to pass assuming the timing is reasonably correct now, and if you or no one else understands the NOx control system, you're going to be on your own.

If the car has an EGR system the valve and control system should be tested. If there is no available documentation on how it works or the parts used, you or someone is going to have to figure it out.

Prior the the introduction of three way catalysts (TWC), which both oxidize HC and CO and reduce NOx, NOx control was achieved with EGR and timing calibration or some combination of the two. Prior to TWCs oxidizing catalysts (OC) could oxidize HC and CO, but not reduce NOx.

The first TWCs were introduced about the time your car was built. Cars certified to meet 49-state or CA emssions have codes on the emission/tuneup label in the engine compartment for the basic emission control equipment and will indicate if the car is equipped with OC, TWC, or EGR.

So what emission control equipment codes are listed on the label?

Duke
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  #3  
Old 08-02-2004, 05:42 PM
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Duke is right. You need to understand what was stuck on the car to make it comply.

If it has an O2 sensor driving a frequency valve, that may be part of the problem. If you have an EGR valve, that's a suspect.

Lots of good posts - do a search on "emissions and nox"
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Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #4  
Old 08-02-2004, 11:32 PM
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280 SEL Failed Emissions Test High NOx

The car is Gray market. I do not have the emission records from 2 years ago and it does not have an emission label anywhere engine compartment or door panel.
I removed the EGR valve and it is stuck closed indicating no recirculation. There is a sensor mounted in the head with two vacuum ports one goes to the EGR valve one to the switchover valve on the fender well. I think the EGR valve is supposed to open via the temp controlled sensor after the engine is warm to allow recirculation of exhaust gases, I am not sure of the operation of the switchover valve. I only have a Chiltons Manual. I will try to clean and free up the EGR valve and test the vac diaphragm. The car has a cat converter but I am not sure if it is working or what type it is. Do you guys think repairing the EGR valve will reduce the NOx levels the amount I need, 3312 down to 1121?
Thanks very much for the help.
Bob
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  #5  
Old 08-03-2004, 12:20 AM
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Yes, a stuck closed EGR valve can signficantly increases NOx because it's essentially uncontrolled, so if you can get the system operating properly there's a decent chance that NOx will drop below the limit.

Your HC is a little high, but CO is low, so your mixture is okay and the converter appears to still have some effectiveness. The hotter the converter the more effective it is, so make sure the car is fully warmed up and the converter good and hot before it's tested.

I CA I recommend drive through emission test stations. Go to one that has a short or no line with the car good an hot, and keep it running at 1500-2000 before you hand it over to the tech. The M103 engines and some other KE-equipped engines have been tagged "high emitter profile" and many are on the ragged edge or marginally fail, so "managing" your test and "conditioning" is important. My data indicates that the converter can cool off significantly after a few minutes of idling.

Duke

Last edited by Duke2.6; 08-03-2004 at 12:25 AM.
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  #6  
Old 08-03-2004, 11:40 PM
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Duke, Chuck,
Thanks for the help. I cleaned and checked the EGR valve. It was only dirty and the diaphragm worked OK. Duke you are probably right on track with fraudulently certified because I found a ball bearing stuck inside each vac hose to plug the lines and stop the EGR from opening. After removing the bearings I went back to the E test station and failed again. This time with the EGR working the NOx came down to 2010 but still not enough and with the EGR working the car ran very rough and almost stalled. For now I will just park the car because I do not want to put alot of time/money into making all the other repairs needed along with passing the E check and I only drive it in the winter.
Thanks again for the help,
Bob
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  #7  
Old 08-04-2004, 02:02 PM
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If the engine almost dies with the EGR connected, then the valve is probably bad and allowing a massive vacuum leak.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #8  
Old 08-04-2004, 04:28 PM
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The other issue is that EGR should only function at part throttle cruise, not WOT or idle, so check the control system, but being gray market there is no guarantee that the EGR system was properly engineered.

Duke
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  #9  
Old 08-05-2004, 11:28 AM
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If you itemize and file the long tax form, my suggestion would be to donate the car to a charitable cause. With the new dyno testing and tighter emission laws, it is tough enough to get U.S. versions to pass. You probably have a home grown computer stuck under the dash to control the frequency valve. If that craps out, where are you going to get another one. The grey markets were fine in their hay day, but the hand writing is on the wall. I think this car could bury you with time and money. In fact the money and effort you put in could go to getting you into a nice U.S. version. That is just an opinion coming from a 30 year factory trained MB mechanic.

Good luck,
Peter
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  #10  
Old 08-05-2004, 11:08 PM
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Get it registered in Alabama.
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  #11  
Old 08-06-2004, 08:35 PM
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The car runs fairly decent and I only used it as a winter driver, thinking eventually I would make the repairs it needs. Since it will not pass the E check I will just park it for now. It needs several repairs to bring it up to good condition, and I don't feel it is worth the money or time. I could use the money finishing the work on my 380.
Thanks for suggestions/help.
Bob
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  #12  
Old 08-07-2004, 12:26 AM
Benzman500
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One thing not mentioned is the fact before 86 it was much easier to get a car into the USA. If you write the EPA with your vin you can try to get the forms that the car had filled out to get in offically.
What grade gas do you run. A lot of bimmer guys find high test helps them pass emmisions a little easier. Do you have a cat installed?

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