I don't like the sound of your duty cycle readings. Fluctuation is normal. In fact, if it doesn't fluxuate there's a problem. MB service data says the average duty cycle at idle should be within 10 percent of the duty cycle at 2000 revs, no load, so if you eyeballed an approximate 45 percent at idle is should average no more than about 55 percent at 2000.

Other's have reported results similar to yours, but it's never been clear to me what causes the duty cycle to drop and stay near 10 percent.

There is either a problem with the system or with your measurement technique. On my '88 CA car I have to manipulate the button on the X92 connector to place the system into "test mode" to measure the duty cycle, but I don't think that applies to your car.

Duke

It is not what I had expected to see.
The reading was taken at idle with the car warmed up. If I disconnect the oxygen sensor it goes to a steady 50.x%, as it should, with no fluctuation.
The car seems to be running very well so I think I will take it to the inspection on Tuesday and see how it reads.
I will report back then with the results.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

After:
New water temp sensor.
New Cap & Rotor.
Oil change.
Techron still in tank during test.
Fully warmed up...(run at close to 4000 rpms for about half an hour in advance of test)

Mode-----------CO%---------------HCppm-----------------RPM-------Dilution
2speed idle---Limit-Reading-P/F-----Limit-Reading-P/F---Read-Resu-Read-Resu
Idle----------1.2---7.25----Fail-----220--468----Fail----684-Valid--17.8-Valid
2500 rmp----1.2---6.27-----Fail-----220--254----Fail-----2531-Valid--17.4-Valid

Some additional facts:
I have yet to put in the new O2 sensor...
In the course of my investigation I discovered a leaking EHA
I suppose the cat could be called into question as well.

The low duty cycle seems to point to a problem...
One strange thing, when I test duty cycle Ignition on engine off I should get a reading of 70%-49 states car, but I get a reading of 30%?
Duty cycle engine on starts at approx. 45% then descends slowly down (over about 5 min) to the 8-12% range where it hovers (fluctuating)
If I pull toe O2 sensor lead I get 50% but if I pull the water temp sensor I get 70% not 30%?

Any advice/support appreciated. (we'll get her through this... the EHA alone will buy the waiver)

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

Your CO reading indicates a very rich mixture. Likely there is something wrong with the lamda system, but it could be almost anything associated with the system.

Once you find and correct the problem with lamda, the CO should be no more than about 0.5% If more and HC is still high the catalyst may be called into question.

Duke

Hey I work as an emissions tester for my area. I will tell you this much, once a mercedes turns 10 years old, you better pray it passes. I see alot of Mercedes that are over 10 years old FAIL. I have a C Class mercedes which FAILED when it was only 8 years old, turned out my CAT. had unmounted from its proper postion, and that simple fixed passed me. The problem with Mercedes and Some Volvo's is they come with horrible CATs, and expensive to buy and replace. Also some mercedes models have questionable Air Mass Meters that were made by Bouch and this alone can simply mess your car's exhuast emissions to a point where you will not pass since your car's not operating properly. I personally think its your CAT, you will need to replace it inorder to pass. This is very common on mercedes, and I've had some people tell me its costs them an arm and a leg. So give your CAT and Air Mass Meter a check, and you'll have your car on the road again. Hope this helps.

p.s. One of the Volvo's that failed last week. The tech told me he knows their cat's suck, that's why we all drive chevy's at our dealership....

I would expect a better analysis from and emission test tech. Don't you have to go through some kind of training? As a former emissions research engineer, I can assure you that I had LOTS of training.

I fail to find a cause and effect relationship between catalyst mounting and catalyst effectiveness, unless you are taking about a leak, which would cause a noticeable noise.

The CO indicates an A/F ratio of less than 12.5:1. The lamda system should keep the A/F near 14.7:1, which would yield CO below one percent even if the car had NO catalyst at all. An over rich A/F to this degree will prevent the three wasy catalyst from energizing any oxidation or reduction reactions.

I suspect that a lot of properly performing catalysts get replaced due to this type of faulty analysis. Catalysts do degrade with time as I've pointed out in previous posts, so "conditioning" becomes important, which is an owner responsibility.

http://www.peachparts.com/shopforum/tech-help/117048-successful-ca-asm-emission-test-ke-fuel-system.html#post833484

The owner needs to fix the lamda system first and only judge the catalyst performance when the lamda system is functioning properly.

The car in question does not have a convential hot wire anemometer MAF sensor like a "modern" car, but its mechanical air flow momentum sensor should be checked for proper operation.

Duke

Thanks for those directions
I am beginning to suspect something directly related to the fuel metering ... the air flow sensor, EHA, or the distributor itself.
The leaking EHA is immediately apparent.
I am hoping its replacement gives me the duty cycle I am looking for.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

If you have not already done so, go to the following site and download the complete 103 engine manual. Also download all the fuel system info from the 124 CD. Study the information so you understand the system, then refer to the various tests and repair procedures.

http://mb.braingears.com/default.htm

The KE fuel system is complicated, but logical, and once you have sufficient "system knowledge", you should be able to troubleshoot and isolate the exact problem. It makes a lot more sense to approach the problem this way rather than guessing and throwing parts at it hoping that you eventually solve the problem

Duke

Call me an idiot.
I guess I missed a very basic step when checking duty cycle.
Red Banana (+) needs to be in the #2 terminal.
Black Banana (-) needs to be in the #3 terminal.
I had it reversed. I just assumed, incorrectly, that it was the other way around. So my readings were the opposite of correct; except for O2 sensor pulled (the opposite of 50% is 50%).

Anyway my new readings make more sense:
Ignition on engine off = fixed 70% duty cycle (or 69.8% fixed)
Idling (fully warmed up) reading fluctuates and climbs to over 90% (trying to lean)

Replaced seals in the EHA… still leaks.

Replaced O2 sensor… and first I have to say again, “I am an idiot”.
I had leaned it out a little, earlier, at the tower to see if the duty cycle would respond… it did not…
So I replaced the O2 sensor and tried to measure duty cycle with the Red lead still plugged into the Amps socket! and got a steady 92%… very confusing.
Once I figured out my mistake and fixed my meter I was still getting a high (lean duty cycle and thought I had not solved anything with the O2 sensor… very depressing.
Trying to richen the mixture at the tower it felt like it was not turning the adjustment screw and I thought I was screwed… until I realized I had grabbed the 2.5mm Allen key instead of the 3mm… ¼ turn later I had a fluctuating duty cycle in the high 40’s%

Thank you all, particularly Duke2.6 for hanging with me through this, for me, very educational process.
I will post my emission results when I get the retest.
Till then…

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

How much $$$ have you spent so far to get your car in compliance? I found a FAQ on the www.drivecleanpa.state.pa.us website that states you can get a one year waiver if you have spent $150 or more to bring your car into compliance:

What happens if a vehicle fails the emissions inspection?
If a vehicle doesn’t pass the emissions inspection, you must make emissions-related repairs. After these repairs are made, the vehicle can be re-inspected for free, within 30 calendar days, at the station that initially conducted the inspection. If you wait longer than 30 days, or take the vehicle to a different emissions inspection station, the reinspection is not free. In addition, if the vehicle still doesn’t pass the inspection, in most cases you can get a one-year waiver if you have spent a minimum of $150 on emissions-related repairs. In some cases, you may be required to spend more if the needed repair is the only repair that will address the problem. Check.

__________________
2002 500SL(Black/Black)
1992 300SE(Black/Black)
1992 190E 2.3(White/Navy)
1999 VW Jetta TDI(Pearl Green)
1986 SAAB 900 Base 3 door(White)
1983 Porsche 911SC(Chiffon)
1977 VW Scirocco(DiamondSilver)

I am aware of the $150.00 waiver... but my real goal is to get her right.
I am up to about $160.00 so far (Cap & Rotor, Mustang O2 sensor, and water temp sensor)
I missed my first free re-inspection when the fan clutch bearing bracket failed and the job (mostly finding the right used part) took me 33 days.
The engine has never been cleaner as taking off all that stuff gave me the opportunity to scrub off a lot of gunk.
Based on my duty cycle though... I think I might have her in spec.
I think my gas savings over the year might cover the cost of the repairs... and I have a Toyota PU from my work that will get me around till I can get her on the road. Sure do miss the Benz though... but knowing she is running great will make our reunion all the better.
Thanks for your thoughts.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

Mode-----------CO%---------------HCppm-----------------RPM-------Dilution
2speed idle---Limit-Reading-P/F-----Limit-Reading-P/F---Read-Resu-Read-Resu
Idle----------1.2---0.26-----Pass-----220--191----Pass----703-Valid--15.0-Valid
2500 rmp----1.2---0.29----Pass------220---49----Pass---2580-Valid--15.0-Valid

Once again...Big thanks.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

Your effort was exemplary and proves that following a systematic troubleshooting procedure will eventually get you to a solution, and this is certainly better than replacing parts willy-nilly or buying a bottle of "smog test in a can" based on guess work, which seems to be pretty common, both among DIYers and professional shops.

Since the service information for these engines is available on-line and can be downloaded for free, there's no reason not to follow this approach and educate yourself on the system operation and use the published troubleshooting and diagnostic procedures. Of course this takes time. Some expect a silver bullet from the Board, but there aren't any to pass out.

Your HC at idle is still high and would probably fail the CA two-speed no load test that is used in some areas of the state that don't have significant air quality problems. Before the loaded dyno test was phased in back in '99, we had the two-speed no load test. The 2500 RPM test was run first.

Do they run the 2500 RPM test first in PA?

This would help heat up the catalyst, but my car's idle HC count was always higher at idle and on the ragged edge of the limit a couple of times. There was probably still enough O2 in your car's exhaust to enable more oxidation if the catalyst was hotter, which is why "conditioning" is important, especially as the catalyst slowly degrades with operating time accumulation.

One way top keep the cat hotter is to understand the effect of ignition timing on both EGT and peak flame front temperature, which is the source of NOx.

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

Duke

They run the idle test first... at least where I went they ran it first.
Unfortunately due to scheduling constraints this time, I left it for them.
I imagine it had been sitting for at least a half an hour... after listening to the engine, looking at the duty cycle, and sniffing the exhaust I was confident enough to leave it there for them to do their worst.
Besides which I had already exceeded the $150.00 emissions repairs amount to buy a waiver if it had failed.
It passed the first time through.
If you fail the first test here in PA they do a "preconditioning" (top off the oil if necessary, and rev it at 3000 for 3 minutes before doing a retest. If you fail the retest with "preconditioning" you have 30 days to get a repeat of the whole procedure at no additional cost.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

Hey there,

Thought I would chime in in regards to your catalytic converter since I went through a similar situation with my non MB vehicle.

If you are running rich to the point that your mpg's and power have dropped considerably there is a strong likelyhood that you have cooked your catalytic converter.

__________________
1979 Thistle Green 300D 272,xxx miles
1984 Orient Red 300 D 4 spd Euro Import - 189,xxx miles
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