Today I decided to smog my car. I was going to wait until I replaced the O2 sensor but after reading even more posts about them I decided to just go and see what the outcome was.

Well, my car passed, which means that my O2 sensor works so I won't have to worry about that. The only catch was that my gas cap failed so I bought one on the spot and used it to pass. The tech opened a drawer filled with MB gas caps, said that they all fail, that sucks. Here's the results, they seem good, at least I think so

HC CO NO
Test - Max - Ave - Meas - Max - Ave - Meas - Max - Ave - Meas
15 - 105 - 31 - 49 - .69 - .10 - .06 - 757 - 237 - 90
25 - 80 - 20 - 23 - .56 - .09 - .04 - 696 - 199 - 25

Test - %CO2 - %O2
15 - 14.9 - 0.0
25 - 15.0 - 0.0

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

Probably all you needed was a new fuel cap gasket.

It would help if you stated the year/model/engine.

Duke

HaHa, I seem to always forget that It's a '92 400E

I thought that my gas cap would pass since there's always a loud suction when I remove it to fill the tank, but guess I thought wrong.

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

Put the year and model in your signature along with that a... phase.

Okay, now on to emission analysis. Your emission control system is working as well as it can as indicated by the zero percent O2. As with most Mercs of this era, the HC is above average for the year group. Many are at the ragged edge of the limit. Also, FWIW, the NOx is commendably low.

The numbers for a 400E probably don't get much better than what yours achieved.

Duke

Zero, or Duke if you know, was the M119 classified as on of the HEP vehicles?

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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

Good question, Mike, I meant to ask it.

zeronero: Look on the top of the report, "Vehicle Information" - last item in the RH column - "Inspection Reason". What does it say?

Duke

Says "HEP"

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

Yeah, that's what I figured. I've been tracking all the emission test posts, particularly in CA. I think ALL the KE equipped engines have been tagged HEP. A continuous flow mechanical FI system, even with the electronic enhancements -O2 sensor and EHA - just doesn't provide good enough fuel control to make low HC numbers and the system is devilishly complicated compared to a pure digital system with solenoid injectors.

In the case of marginal failures there is likely nothing really wrong with the car. The owner just didn't "manage" the test properly. The key is to have the converter as hot as possible so it operates at peak efficiency and uses as much of the available oxygen as possible.

This means going to a drive through place after the car has run for at least 20 minutes, preferably with a freeway jaunt. Go when the line is short and keep the revs at 2000 until the tech is ready to take the car. If possible go on a rainy day and ask them to run the tire dry procedure. They run it on the dyno with no load at about 25 MPH for about a minute. This will heat up the converter. When I did this trick two years ago the HC at 15 MPH dropped to the mid-eightes from barely passing low one hundreds the time before. Since my test is due early in the year, I think I'll keep waiting for a rainy day to test.

Duke

Duke 2.6

FWIW, where I live, you don't have to wait for a rainy day.
The test stations run a " conditioning cycle " ( 25 mph for 90 seconds ) & only then proceed with the actual test.

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2007 C 230 Sport.

Here is CA there are some shops that will do a "pre-test" and I think this includes some "pre-conditioning". I'm not sure of the exact rules that allow this, but, of course, you pay extra for the pre-test.

So far I've not failed just going to a drive through, but I've been a couple of PPM from busting he 15 MPH test.

Duke