Euro 500SEL illinois emissions test problem - PeachParts Mercedes-Benz Forum

agara · #1 04-29-2004, 04:46 PM

Well, failed my Illinois emissions test. Vehicle is 1984 500SEL euro model. The car did have catalytics spliced into the system when it was brought over, and this version has no lambda adjustments possible. Illinois does a simulated city/highway drive and unfortunately provides their numbers in "GPM", not %. Any help on how to convert would be extremely helpful. The O2 sensor was messed up so that caused pretty bad readings. Not sure why I took the test in the first place, I knew it was idling a bit dodgy. Oh well on that one.

Anywho, I replaced the O2 sensor, plugs, wires, did a fresh oil change, and double checked the lambda %duty which is reading what to book says, though I can't change it anyway. The sensor cable was buggered up so I replaced that all the way into the box. I'm doing the retest tomorrow. At this point the car idles and runs as smooth as it ever has so I'm crossing fingers.

Question is, has anyone had an 80's euro model pass emissions test in Illinois lately? I'm wondering if this model will pass the fancy test at all. The limits they give, for whatever it's worth, are HC max 2.00 GPM, CO 30.0 GPM, no limit on CO2. I don't even know how they measure GPM on a complex mixture of HC in the first place. Must be interpreted some how.

manny · #2 04-29-2004, 05:20 PM

Can you tell us what your readings were?
Also, I don't believe there is an accurate way of translating "GPM" into percentages or ppm.

agara · #3 04-29-2004, 08:06 PM

My readings were with a faulty O2 sensor, so they're pretty useless as far as I can tell. Also, they are in GPM, so not sure how to use that.

HC=6.81 (limit 2.0)
CO=279.1 (limit 30.0, says "composite")
CO2=418.1 (not judged, just measured)

However, I bought the car from a guy in FL, and have four years of his records. Readings from FL are direct and I think at idle.

HC=36, 66, 79, 133 (limit 220PPM)
CO=.01, .00, .07, 1.19 (limit 1.2%)
CO2=14.4, 14.1, 14.4, 14.3 (no limit %)

Listed readings are respective (e.g. 36, .01, 14.4 was on set). If I knew what the GPM readings corresponded to in % then I could at least figure out if I'm in the ballpark.

manny · #4 04-29-2004, 08:56 PM

You didn't fail the test, you bombed out.

After all the tune-up work & O2 sensor replacement you have done, it's probably worth giving it another shot.
How much are they charging you each time?
If you still have trouble passing, unfortunately it may be time to suspect the effectiveness of your 20 year old catalytic converter(s).
I noticed the previous owner was walking a thin line on CO as well.
As I said before, you really can not calculate grams per mile into percentages, as they are two totally different tests.

agara · #5 04-30-2004, 10:04 AM

Strangely, the last FL readings were the 66/.00/14.1. He must have done something after the high reading. Thankfully the IL-DOT does not charge for emissions testing. A nice woman at the DMV told me that if you accumulate enough $$$ spent trying to get you car up to snuff, and there's nothing actually wrong with the emissions system (via mechanic affidavit) they will waive testing. She also drove a 1984 300SD and was extremely sympathetic.

A full new exhaust system is in the works, and I hope I don't have to get it to pass this test. I've been holding off on getting an exhaust system out of this fear that they car (being euro with no US emissions related hardware) will not pass IL testing no matter what. That means selling the car with what will surely be a >$1000 new system. I have to get a euro exhaust then have universal catalytics spliced into each side. US made exhaust is apparently completely different and not interchangeable.

ctaylor738 · #6 04-30-2004, 10:27 AM

Is there no mixture adjustment (top of fuel distributor) that you can use to tune the on-off ratio?

agara · #7 04-30-2004, 11:16 AM

There might be. I can't remember all the details at the moment, and my manual is at home. If memory serves, there is a certain pin missing on the engine test connector interface that was required when adjusting the mixture. While going through the lambda diagnostics section, there were a couple things that just didn't appear on the engine that were shown to on the US version. I will have to pull up the manual and try and remember the details. I am sure there is a mechanical adjustment, but (from bad memory again) the numbers I read were within spec so I didn't need adjustments.

This model is an early euro 1984. No leather, no grey plastic side panels, no plastic bumper covers (big heavy fiberglass airdams), old school 14" turbine type rims, no hydraulic suspension.

agara · #8 04-30-2004, 11:21 AM

There might be. I can't remember all the details at the moment, and my manual is at home. If memory serves, there is a certain pin missing on the engine test connector interface that was required when adjusting the mixture. While going through the lambda diagnostics section, there were a couple things that just didn't appear on the engine that were shown to on the US version. I will have to pull up the manual and try and remember the details. I am sure there is a mechanical adjustment, but (from bad memory again) the numbers I read were within spec so I didn't need adjustments.

This model is an early euro 1984. No leather, no grey plastic side panels, no plastic bumper covers (big heavy fiberglass airdams), old school 14" turbine type rims, no hydraulic suspension.

ctaylor738 · #9 04-30-2004, 11:36 AM

Even without a lead to the test socket, you should be able to hook up a DMM with a duty cycle function to the positive lead to the frquency valve and get a on/off reading. Assuming of course that there is a frequency valve.

There should be a hole in the air cleaner where you insert a long-arm 3 mm allen wrench to adjust the mixture.

agara · #10 04-30-2004, 11:58 AM

Yes, this part I did when checking all the functions. The duty was right on spec, measured with a scopemeter at the test socket. I feel kinda dumb at the moment since I can't remember what was different on the ECU systems. Obviously it wasn't the mixture screw. It had to do with the actual ECU system.

Hatterasguy · #11 04-30-2004, 12:05 PM

This is a little dishonest, but I know people who have gotten old cars to pass CT emissions with rubbing alcohol. But it is better than selling the car, or you could try some of those chemicals they sell at autopart stores.

agara · #12 05-03-2004, 01:09 PM

Well, went back to emissions test facility, crossed my fingers, and passed fine. Happy ending. I would submit readings, but IL now measures in "grams" not gm/mile like the last time I took the test. Numbers are useless to even compare to previous test. In any case, I was pretty comfortably within the limits. So if anyone does a search in the future, a 1984 euro W126 500SEL with aftermarket catalytics will pass IL-DOT's super fancy "real world driving" emissions test.

I appreciate what the IL-DOT is trying to do simulating real driving conditions as opposed to static speed/rpm. However, it is very unfortunate that you don't get an actual % measurement out of it. Kind of a free engine diagnostic that most DIYers can't easily get.