'92 500 SL Fails CA Smog - PeachParts Mercedes-Benz Forum

Mike Miller · #1 09-25-2006, 01:15 PM

I hope Duke (Duke2.6) reads and responds soon. I failed emissions for high HC.

Idle 732 rpm CO2%=8.60;O2%=0.00;HC (PPM)MAX=120.00;AVG=29.00; MEAS=187.00;CO2 (%)MAX=1.00;AVG=0.10;MEAS=0.05
2500 2378rpm CO2%=14.60;O2%=0.10;HC (PPM)MAX=140.00;AVG= 20.00;MEAS=201.00;CO2 (%)MAX=1.00;AVG=0.10;MEAS=0.24

I was tested as a "High Emitter Profile". All other systems passed. The test computer program automatically directed a "conditioning run" at 2500 rpm for three minutes. Then it re-ran the idle and 2500 rpm tested. Final result = FAIL. The tester thought I had a slight miss at 2500 rpm test. I can't see or feel it. The car runs great.

I went back to my indy garage. They put a new set of plugs in and "leaned out" the fuel distribution valve. I have relatively new rotors (one year old). The caps are original as are the plug wires. We aborted the second emissions test just prior to a second "conditioning" run. The tester said when the computer tells you to do a conditioning run, you are almost garranteed a failure. I did not want to end up a "Gross Poluter" with the DMV.

I know you have gone through this with other owners, but I am hoping for some words of advise as to areas to look at.

Jim B. · #2 09-25-2006, 01:50 PM

They have changed the rules on us with the "Test Only" smog test stations.

I don't know how things work now, but is there any chance that your Indy mechanic can tweak the car * and * then TEST the car so it passes, or are you going to have to go to another smog shop to get the car re tested?

Under NO circumstances do you want it branded a Gross Polluter - that's really like the Scarlet Letter, you don't want to go there...

Do all you can to be sure it will pass before you hook it up to the sniffer for the second time. I think the results get fed DIRECTLY to the Sacramento DMV.

I had a friend with a 380SEC whose car, several years ago, got branded a Gross Polluter simply because the idiot tech at the smog test center accidentally pushed the wrong buttons on the computer!! It was like, have you read any Kafka lately? What a mess. Many $$$ to sort out, much aggravation and it wasn't even his or his car's fault.

Duke2.6 · #3 09-25-2006, 01:55 PM

You live in HB, but the test was the two speed no load. HB should be ASM. What gives?

I'm not aware of the "conditioning", but that may be a change to the two-speed test, which hasn't been run on any of my cars since they went to the ASM test for non-attainment areas.

I assume your engine has the KE system, and adjusting the mechanical mixture must be done using the duty cycle method, not "by ear". If the basic setting is so lean that the system runs out of control authority, lean misfires could occur that will increase HC count. Your idle O2 at 0.00% says all the oxygen is being used by the catalysts, so lean misfire is the most like cause of the high HC at idle.

At 2500 there is still a little O2 left, but even if it's all consumed, I think HC might still be high, which, again, indicates an occasional misfire.

The first thing to do is check that the duty cycle is in spec, and a scope check of secondary wave form should show if there are misfires. Also, be sure the correct non-resistor spark plugs are installed.

You should also review my previous discussions, and as a last resort you can change the spark advance map.

http://www.peachparts.com/shopforum/showthread.php3?p=833484#post833484

The C02 percent at idle doesn't make sense - should be higher and you confused CO2 with CO.

Duke

Mike Miller · #4 09-25-2006, 04:32 PM

Duke,
Thanks for the quick response. I am struggling here.

I don't know what ASM means. I do know the test was two speed, no load. I didn't question it. What the heck do I know about CA Emissions requirements, tests and least of all my 500 SL. This is the first Merc I have ever owned and a complicated one at that.

How do you adjust mechanical mixture using the "duty cycle" method. My indy did it by ear, which you say is wrong. Getting into a "scope check" of secondary wave form is going past my indy's technology base unless you are talking about surfing

I do know the plugs are non-resister type.

Sorry about the CO/CO2 screw up. I was trying to get it on the page so it made sense. I transposed it too many times. You are correct, the last reading are CO not CO2.

Mike Miller · #5 09-25-2006, 04:35 PM

Duke,
The post you send in your last response does not open. Shop Forum says it can not be found.

Duke2.6 · #6 09-25-2006, 10:40 PM

The link must have changed. Do an advanced search of threads started by me with the word "emission".

This basic thread has several links, one of which is the procedure to set the basic mixture using duty cycle.

ASM is "acceleration simulation mode" - the chassis dyno test - and is a requirement in all "non-attainment" areas, which includes Huntington Beach. So, how is it your car only got a two speed idle test. What city is it registered in and where was it tested?

Most independent shops should have an ignition analyzer scope to evaluate secondary wave forms. I don't see how a guy can be in business without one, and you either need to set the duty cycle yourself or find someone who knows how to do this procedure. All you need is a 30 dollar Sears multimeter with a duty cycle function.

Duke

Mike Miller · #7 09-26-2006, 06:44 PM

Duke,
If the ASM is "acceleration simulation mode" - the chassis dyno test and is required, would my car have passed using it rather than the static idle/2500 rpm test? Why would he not used the right test?

Mike Miller · #8 10-03-2006, 08:50 PM

I changed my distributor caps and reset the "duty cycle" to approx. 45%.
The car has never run better. There must have definitely been a miss that I could not detect.

Next stop..........Smog Tester!!!

This better work or I am screwed.

Duke2.6 · #9 10-03-2006, 09:16 PM

Quote:

Originally Posted by Mike Miller

Duke,
If the ASM is "acceleration simulation mode" - the chassis dyno test and is required, would my car have passed using it rather than the static idle/2500 rpm test? Why would he not used the right test?

ASM adds NOx testing because the engine is under load. There is little NOx at no load. If you bust a two speed no load test for HC it will probably also fail HC on the ASM test.

In what city are you having the car tested?

What was the idle and 2000 RPM duty cycle before you adjusted it?

Let us know the test results.

Duke

Mike Miller · #10 10-04-2006, 09:02 PM

Quote:

Originally Posted by Duke2.6

What was the idle and 2000 RPM duty cycle before you adjusted it?

Let us know the test results.

Duke

I believe idle duty cycle before adjustment was averaging around 37%. I was by myself so not sure what was at 2500 rpm. There really isn't enough room under my little shade tree for too many more mechanics!!! I was just hoping for some kind of improvement that I could see and feel.

A VERY rough indicator also was my MPG guage. Not the best troubleshooting tool, but a very interesting outcome. Driving home on the freeway yesterday. I noticed that at steady state (or as close as I could maintain) 65 mph, my MPG gauge now reads around 20. Before new rotor caps and duty cycle adjustment, I would see more like 15 -17 at best. I will fill up again on Friday. I am expecting a 3-4 mpg improvement in fuel consuption, if not more.

I will let you know the results when I go to test.

Tomguy · #11 10-04-2006, 10:00 PM

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

This is the link Duke tried to post in WORKING form. Duke is still using php3 to access the ShopForum even when the webmaster announced that won't work properly

Mike Miller · #12 10-09-2006, 07:45 PM

Crap!

Now they tell me I might have a problem with an injector. Or maybe bad plug wires. Why does this car run so darn well and still have a problem

Mike Miller · #13 10-14-2006, 12:29 PM

Any opinions??????????

deportes · #14 10-16-2006, 09:59 AM

My 92 500 sl was CA smooged 6 months ago and the reason it wasn't dyno tested was that he couldn't disconnect the anti slip system.

My car had a slight miss which I was worried about but the car passed with flying colors. The caps and rotors were in pretty bad shape. But I finally found that the idle miss was due to the mixture air/gas. I adjusted it last week and now it idles great. Still running with old rotors but I cleaned them out.

Now I need to understand the duty cycle adjustment and how you perform it.