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  #1  
Old 04-11-2005, 10:44 AM
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'94 E420 failed CA smog, What's up?

My E failed smog. 113,000 miles. It passed at 15 mph, but failed at 25 mph. Didn't fail by much. No codes on the computer. I've noticed a slightly rough idle recently.

The smog guy suggested a new O2 sensor and plugs. He also said that the catalytic converter rarely goes on these cars.What to do? Shell out the $150 for the sensor? I'm lost.

Thanks.

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1994 E420, Pearl Black/Black. 2.82 rear diff., AMG front spoiler, painted lower half. SOLD

1972 & 1974 BMW 2002tii's.
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  #2  
Old 04-11-2005, 11:48 AM
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I'm sure Duke will be along shortly to interpret your test, so I'll say it now - post the numbers from the test results, and if it all possible the numbers from the prior test (2 years ago).

It is impossible to even venture a guess without seeing any numbers.
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  #3  
Old 04-11-2005, 11:54 AM
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Here they are. 2 Years ago, no dyno test, this year it was.

2 Years ago:

HC:
647rpm: 12
2556rpm: 13

this year:

15mph, 1446rpm: 46
25mph, 1258rpm: 64, allowed is 47

Craig
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1972 & 1974 BMW 2002tii's.
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  #4  
Old 04-11-2005, 12:13 PM
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I don't know if there is anything wrong with your car until I see the COMPLETE test results.

Read the following thread, and the thread it refers to, then post your complete test results in the format I used. You will know enough by then to do your own analysis, so tell me what you think, and I will give you my comments.

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

Duke
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  #5  
Old 04-11-2005, 02:48 PM
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If you were close I'd be willing to bet that you would pass with either 1) new plugs, or 2) a bottle of "guaranteed to pass" (follow directions). Do both 1 and 2, about $20 total and it won't even be close.
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  #6  
Old 04-11-2005, 09:25 PM
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OK, here goes again:

2 years ago:

RPM: 647
CO2% Measured: 15
O2%: .1
HC, Max: 100, AVE: 17, Meas: 12
CO% Max:1.00, AVE: 0.00, Meas: 0.00. PASS

RPM: 2556
CO2% Measured: 15
O2%: .2
HC, Max 130, AVE: 12, Meas: 13
CO% Max:1.00, AVE 0.10, Meas 0.02 PASS

Last week:

RPM: 1464, 15 mph.
CO2% Measured: 14.4
O2%: .07
HC, Max 81, AVE: 21, Meas: 46
CO% Max: 47, AVE 0.05, Meas 0.09
NO: Max 685, AVE:150, Meas: 283 PASS

RPM: 1258, 25mph.
CO2% Measured: 14.3
O2%: .1
HC, Max 47, AVE: 12, Meas: 64 FAIL
CO% Max: .44, AVE 0.05, Meas 0.14
NO: MAX 696, AVE: 136, MEAS: 270

From your write up before, it looks like my cat was warmer 2 years ago that it was last week.
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1994 E420, Pearl Black/Black. 2.82 rear diff., AMG front spoiler, painted lower half. SOLD

1972 & 1974 BMW 2002tii's.
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  #7  
Old 04-11-2005, 10:21 PM
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Well your test results do not quite fit into the "norm".

Usually the HC problem is at 15 MPH when the catalyst is cool, but the 15 MPH test heats it up so the 25 MPH numbers are lower. It looks like your test two years ago was a two-speed no load test, so you must live in the Bay area where the ASM test was just implemented last year. Even though the previous test was no load, there appears to have been an increase in emissions. What was the odometer reading for the two tests? This could be a case of catalyst aging, but it's not that bad!

You have a bit of O2, which means that if the catalyst were hotter there would probably be more oxidation reaction, so If you know how to alter the ignition advance curve for your engine, that will probably do the trick.

I know how to do it for M103 engines, but I'm not familiar at that level of detail with the '94 fuel and igntion systems, so I can't give you any specific "how to" advice for your model.

The CO tells me that the mixture is within the stoichiometric sballpark, so I don't see an O2 sensor problem, but I would want to look at its wave form on a scope to determine if its response time has degraded. Most shops will just want to replace the O2 sensor, and that may help or not. See the nearby thread where someone had the catalyst replaced and the emissions INCREASED.

There is no substitute for good analysis and testing beginning with understanding what the data on the test report is telling you. You would think that these mechanics were never taught this information. They were, but you would never know it. Most of them seem to have forgotten everything they learned when they got back to the shop and back into the old routine of swapping parts for an hourly rate until they end up fixing the problem, if they ever do before the customer walks off in a huff and trys someplace else.

There ARE good emission repair techs out there, but they are damned hard to find!

Get back to me with the mileage on this and the last test, and also let me know if you the O2 sensor (s) has ever been replaced.

BTW if you were directed to a "test only" station, you can get cost recovery of repairs regardless of your income (don't need to be "low income" to qualify).

Details at www.smogcheck.ca.gov

Duke

PS I'd also like to know the "test weight" for your car and the software version number. Both are on page 1 of the test report. The test weight should be near the top of the report and should be about 300 pounds more than curb weight. The software version number is in the information field just above the signature block. My test on 3/03/05 was version number 0403/ES974825.

Last edited by Duke2.6; 04-11-2005 at 10:34 PM.
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  #8  
Old 04-11-2005, 10:32 PM
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The test 2 years ago was done in Ventura, CA, this latest one was done in LA County.

Mileage 2 years ago was 95,650 and last week it was 113,000. Looking back at my paperwork, the O2 sensor was never replaced. I got the car in 2001 with 90K on the odo.

Craig
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1972 & 1974 BMW 2002tii's.
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  #9  
Old 04-11-2005, 10:36 PM
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Both tests had to be done at test only centers.
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1972 & 1974 BMW 2002tii's.
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  #10  
Old 04-11-2005, 10:38 PM
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Check my additional question in the PS in my previous post.

Also, can you tell me how your car was "conditioned" before you the test run? Did you drive it for at least 15-20 minutes? Did you go to a drive through place with a short line to avoid excess idling? Was (heaven forbid) the engine shut off before the test was run?

Also what was the "inspection reason" - listed top right of the report.

Duke
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  #11  
Old 04-13-2005, 01:53 AM
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I didn't even see the PS, sorry.

Test weight is 4000
SW Version is 310/WP391256

The car just had about an hour canyon drive, stop and go. I took it to a plave without a line, I was the only one. I did turn off the car, for maybe 5 minutes. I didn't know turning the car off was bad.

Does the coolant temp have anything to do with the cat temp? Should I wait for a hot day in the 80's?

Craig
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1994 E420, Pearl Black/Black. 2.82 rear diff., AMG front spoiler, painted lower half. SOLD

1972 & 1974 BMW 2002tii's.
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  #12  
Old 04-13-2005, 02:20 AM
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The reason was HEP (High Emmitter Profile), same as 2 years ago.

Craig
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  #13  
Old 04-13-2005, 08:14 AM
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How much do you have to pay for a retest in CA?
How old are your plugs, rotor and cap?
How long since your last oil change?

You are pretty close... Fresh oil is always a good idea for an emissions test... and you might want to inspect the plugs, rotor and cap if they are fowled up they could make the difference... and might solve your rough idle to boot.

If the O2 sensor is working you dont want to replace, it would be a waste at this point until you know if your sparks are clean and strong.

If you have a multi meter with duty cycle you might want to check out this recent thread by LeaUK:
O2 sensor test and inverse duty cycle
who also has an M119 engine and tested duty cycle to ensure proper range of opperation at the X11 test connector. This will give you a peek into the system and might be able to either rule out or suggest the O2 sensor.
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Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html
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  #14  
Old 04-13-2005, 10:32 AM
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Retest is free in CA within 30 days.
There was a tune up done when I bought it, 2001, 24K miles ago.
An oil change is on my list of things to do.

Craig
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  #15  
Old 04-13-2005, 11:13 AM
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Quote:
Originally Posted by Dcraig
I didn't even see the PS, sorry.

Test weight is 4000
SW Version is 310/WP391256

The car just had about an hour canyon drive, stop and go. I took it to a plave without a line, I was the only one. I did turn off the car, for maybe 5 minutes. I didn't know turning the car off was bad.

Does the coolant temp have anything to do with the cat temp? Should I wait for a hot day in the 80's?

Craig
Coolant temp, within the normal range of operating temperature doesn't have a big effect, but the hotter the better. It's EGT that has the big effect on catalyst temperature. Shutting the engine off prior to the test is a big mistake as this will allow the catalyst to rapidly cool off. As you can see from my test data, even five minutes of normal idling can allow the catalyst to cool significantly. Shutting off your engine, alone, may be the cause of your failure. While waiting, turn on the A/C, open the windows, and keep engine revs at about 1500. You want to place as much load on the engine as possible to keep the catalyst as hot as possible. If the coolant temp climbs up to 100C or above, that's fine. The fan system will keep it from achieving excess temperature. I don't think it makes any difference if the outside temp is 60 or 80 as long as the car is properly conditioned before the test.

High HC with other emissions low can mean an ignition problem. I doesn't take too many misfires to drive up the HC over the limit. On M103 engines high HC can sometimes be improved with a new cap and rotor and new plugs, especially if they have high miles. If your car has a coil on plug ignition system the new cap and rotor doesn't apply, but new plugs might help if the existing plugs are old.

Do you have conventional 30K mile copper core/nickel electrode plugs or does MB specify long life platinum tip plugs for your engine, and how many miles do the plugs have relative to the change interval?

Many think that changing the oil will help emissions. I don't think that really applies unless the oil is beyond the normal service life and/or the engine has high blowby, however, if you are getting close to your next change, go ahead and change it before your retest

Given that you still have some O2 in the exhaust, a hotter catalyst will promote more oxidation reaction. You want to see the O2 at zero, and this will reduce the HC count by 20-30 PPM, but that can only happen if the catalyst is hotter, which gets back to the conditioning issue.

I would go ahead and retest the car. Give it a good warmup drive, go to a drive through test station with a short line and DO NOT shut off the engine, but keep it running while you wait as I stated above.

Duke


Last edited by Duke2.6; 04-13-2005 at 11:34 AM.
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