Our 190E 2.3 just passed CA emissions with the results in the pic.

My concern is the HC emissions at 15 mph, which is 78% of max allowable, despite all other readings being well within the normal range. Would this indicate a marginal injector spray pattern, oil past the seals at high vacuum, normal for this setup, ...?

My concern is to catch an impending failure-to-pass two years down the line. Thanks.

Steve

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__________________
'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

There's nothing functionally wrong with the emission control system. The high HC at 15 MPH is most likely due to catalyst aging and is typical for Mercs of this vintage and many other older cars. As catalysts age they must be at ever higher temperature to catalyze the same amount of reaction as when they were new or near new. Also, O2 sensor response time degrades with age, which can also contribute to increasing emissions on successive tests, but your test results are a classic case of catalyst aging.

Note that the O2 reading at 15 MPH is 0.22%, and it is only 0.04% at 25 MPH. The load from the 15 MPH test steadily increased the catalyst bed temperature, so during the 25 MPH test more of the available O2 was consumed in oxidation reactions, which significantly lowered HC emissions. For every 0.1% reduction in O2, the HC count will drop by about 30-40 PPM, and if the catalyst is operating at peak efficiency (assuming the Lamda system is correctly adjusted and operating properly), the O2 should be less than 0.1%.

The O2 content is a key diagnostic tool. If O2 is high (above 0.1%) at 15 MPH and drops at 25 MPH, along with HC, the catalyst was "cool" at the start of the test and not operating near 100 percent conversion efficiency.

Also note that your NOx is commedably low. Does your engine have EGR?

I have written a TON of emission posts that are in the archives including how to "manage" your emission test, how to understand the gas analysis report and use it as a diagnostic tool, and how to reduce emissions with an aging catalyst that passes by a slim margin (or marginally fails) by altering the spark advance map - including various test results on my '88 190E 2.6 (77K miles, original catalyst and O2 sensor, lamda duty cycle 50-55/40-45 percent @ idle/2000, which means the basic mechanical mixture is a bit rich at idle - better cold starts and cold driveoff prior to going into closed loop mode - but within, barely, the OE spec of 10 percent max variation between idle and 2000.) My last emission test in February gave similar results to those that I reported from early 2005.

Just search suitable terms like "emissions" and my screen handle.

Now I have a couple of additional questions for you.

1. What is your car's mileage, and on what date was it tested?

2. Do you know the history of your O2 sensor - is it original or has it been replaced? If replaced, how many mile does it have, if you know?

2. What is the software version number on your test report? It is printed in the "Smog Check Inspection Station Information" block just above the signature block.

The reason I ask is that I had my '91 MR2 tested last week. The software version is 0703 (March 2007) and O2 is listed only in tenths, not hundreths of a percent. Your car must have been tested with a newer software version, which is now listing O2 to the nearest hundreth of a percent, which is good.

Duke
Retired Emission Control Research Engineer

Thanks for the quick reply, Duke - this is great info. First, to answer your questions:

1) 137k, tested this morning.
2) Far as I know - and I have pretty complete history - the O2 sensor has never been replaced.
3) Software version 310/WP391284.

Temps were pretty warm this morning, better than 85F at time of testing. Drive over was about 15 min, and about a 20 min rest before testing - which went by pretty quickly. The EGR test 'result' is N/A, but far as I can tell there IS a valve. It is bolted to the exhaust manifold, and has a metal pipe leading around to the intake, and a vacuum connection to something.

I was wondering what the high O2 reading at 15 mph signified, so it's nice to know what the mechanism is now. I'll be digging into more of your posts on this. Thanks again!

Steve

__________________
'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

I can't make any sense out of your software version number. All my tests going back to the beginning of ASM testing are yy/mm format. I've never seen a software version number that has only three digits. My 190's last test early this year reported "0.0%" on both the 15 and 25 MPH tests (as did the MR2 last week), but I don't know if the system rounds off or only reports 0.1% when that level is reached. In any event, reporting O2 to two decimal places gives a better indication of how well the catalyst is performing.

Was this a "test only" station, and were you directed to a test only station on your registration renewal?

I use a test only station a few miles away from me in Manhattan Beach. When I brought in the MR2 in last week, two or the three bays were in use and one was open, so I got right in with minimum idle time. There was one car finishing up when the Merc was tested in February. While waiting I keep the AC on Max with the windows open and hold revs at 1500 to keep the catalyst as hot as possible with some load. Minimizing idle/wait time is critical to keeping the catalyst bed hot, and shutting the engine down is a big no-no.

The tech remembered me as the guy with the stick shift six-cylinder Mercedes from early this year.

How many miles does your '90 Accord have, and how does its reported emissions compare to your Merc?

For my '88 model year, Mercedes recommended changing the O2 sensor once only at 60K miles. Mine appeared to function okay at that point, (and still does) so I didn't change it, and the bienniel (soon to be annual if AB 616 passes through the legislature, which it probably will) gives it a health check.

That device on your exhaust manifold is an EGR valve. My '88 doesn't have EGR, (or an air pump), but NOx is still low and VERY low with a retarded timing map.

Duke

Say what!? Oh...yeah. I need to update my signature. The '90 Accord bit the dust recently when a 19 yr/old in a large SUV pulled out in front for a left turn without engaging his eyeballs - in my experience, a rarely used set of driving tools for that age group. Anyway, it failed in march due to ignition timing off, so I had the timing belt replaced at the dealer and timing adjusted (120k miles). Then the results were slightly above average for HC and CO, very small for NO, and 0.0 for %O2, at both 15 and 25 mph. Software version listed as 0403/ES011534. Both cars at 'test only' stations, but different ones.

BTW, in the accident, I slammed on the (non-ABS, disc & drum) brakes and horn, skidding forward into the SUV with a contact speed at my driver's headlamp probably no more than 10 mph. There was no frame/body damage further back than about 10" at that corner. Car drove just fine, no fluid leaks. For a '90, though, the insurance company will not repair. Our replacement for it is a (used) '06 CR-V, which with full collision is only pennies a year more for insurance (and LESS than the 190E), but they will spend thousands more to fix it if it gets a boo-boo. Go figure.

Steve

__________________
'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7