89 260E Fails CA Smog Test - PeachParts Mercedes-Benz Forum

stevenstevensteven · #1 08-16-2005, 12:45 AM

I'd appreciate thoughts from the group on my test results:

Test 1: Friday Aug 12 (Failed due to faulty Check Engline Light)

MPH=15 RPM=1546 %CO2=14.9 %O2=0.1 HC(PPM)=43 CO(%)=.13 NOx(PPM) =762 Pass
MPH=25 RPM=1864 %CO2=14.9 %O2=0.1 HC(PPM)=21 CO(%)=.07 NOx(PPM)=648 Pass

Test 2: Monday Aug 15 (Fixed Check Engine Light)

MPH=15 RPM=1517 %CO2=15.6 %O2=0.0 HC(PPM)=41 CO(%)=.15 NOx(PPM) =948 FAIL
MPH=25 RPM=1714 %CO2=15.5 %O2=0.0 HC(PPM)=14 CO(%)=.06 NOx(PPM)=662 Pass

Any thoughts on where I should begin to source the problem. New 02 sensor and Bosch plugs were installed 3-weeks ago.

Duke2.6 · #2 08-16-2005, 01:21 AM

HC and CO are very good for a M103. Zero O2 means the catalyst was working at high efficiency. The high NOx may mean an EGR problem. You need to do a thorough functional check of the EGR system. Even if it is not working, judicious diddling to the ignition map should lower NOx. My car was low double digit NOx, and it doesn't even have EGR.

Read the following thread and the threads it links to:

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

I hope the "Bosch plugs" are H9DC. That is the ONLY Bosch plug that is correct.

One question: What was the cause of your "faulty" check engine light? Did it yield an EGR code?

Duke

Moneypit SEL · #3 08-16-2005, 01:56 AM

Does the M103 even have an EGR in that configuration? Mine doesn't. NOx is produced when the combustion temperature is high. You might just pass if you short the aux fan switch for constant operation.

stevenstevensteven · #4 08-16-2005, 02:11 AM

"One question: What was the cause of your "faulty" check engine light? Did it yield an EGR code?"

Duke, the Check Engine Light has was simply bad. I replaced the bulb, and the engine light stayed on. I disconnected the battery for a minute, then reconnected, and the Check Engine Light operated normally.

stevenstevensteven · #5 08-16-2005, 02:14 AM

"NOx is produced when the combustion temperature is high. You might just pass if you short the aux fan switch for constant operation."

Moneypit SEL, are you suggesting that I short the aux fan so it is always on? I have noticed for some time that the engine operates at high temperatures. I believe I have a leak or something else that has caused a pressure loss in the cooling system and have not had time to diagnose it. Do you think this high temp operating condition could cause the higher NOx?

MrCjames · #6 08-16-2005, 11:32 AM

Double check all fan operations, contrary to some schools of thought the reality is engine temperature does indeed affect NoX. I have been involved in a number of mid 80’s MB vehicles that did not meet the CA emission standard due to high NoX. Speaking from personal experience get your engine temperature stabilized to around 80C and you should fly through the test. All your other numbers look great

My knowledge is that M103 engines were not fitted with EGR valves until 1990, at least out here in the land of fruits and nuts.

Moneypit SEL · #7 08-16-2005, 01:18 PM

Quote:

Originally Posted by stevenstevensteven

"NOx is produced when the combustion temperature is high. You might just pass if you short the aux fan switch for constant operation."

Moneypit SEL, are you suggesting that I short the aux fan so it is always on? I have noticed for some time that the engine operates at high temperatures. I believe I have a leak or something else that has caused a pressure loss in the cooling system and have not had time to diagnose it. Do you think this high temp operating condition could cause the higher NOx?

Yup. Heat causes NOx. Running the fan for the test may well allow you to pass. Shutting the engine off and allowing it to cool down may also work. There's nothing else in your test numbers to indicate any other type of problem.

What do you mean by 'engine operates at high temperatures'? Do you just think it too high, or did it used to run cooler? What temperature is it running at now? If it engine used to run cooler than it does now, fixing that will fix the NOx.

MrCjames · #8 08-16-2005, 06:50 PM

Quote:

Originally Posted by stevenstevensteven

Duke, the Check Engine Light has was simply bad. I replaced the bulb, and the engine light stayed on. I disconnected the battery for a minute, then reconnected, and the Check Engine Light operated normally.

Are there any DTC's in your system currently? If so you will need to address them. Also, is your fuel injection system adjusted to MB specification? Is the ignition timing correct? Is the vacuum line connected to the EZL control unit? What about your engine temperature? Are you able to get it below 90c? Lowering the engine temperautre will help once all the other factors have at least been double checked.

IMHO: H9DCO (good choice), fuel control set between 40% and 50%, and +/- <10% differential idle vs. high speed (2500rpm)

Always

stevenstevensteven · #9 08-17-2005, 01:56 AM

MrCjames , please excuse my ignorance, but what is a DTC?

Avarec · #10 07-30-2009, 02:13 PM

cant you just put run it real hard, exceding 100+mph for few min to burn off excess engine build up?
it should clear it up a bit

i also heard of adding a pure alcohol in gas tank prior the test

all muscles are fixed this way

compu_85 · #11 07-31-2009, 11:15 PM

Are you sure the fan clutch is working properly? Does the test station have a fan you can direct at the radiator?

-J

stevenstevensteven · #12 08-01-2009, 12:26 AM

Quote:

Originally Posted by compu_85

Are you sure the fan clutch is working properly? Does the test station have a fan you can direct at the radiator?

-J

I have not tested fan clutch, but fan does run at approximately 107C.

necromancer · #13 08-01-2009, 12:28 AM

You might be running a little on the lean side if you are getting high NOx. Check the basic A/F mixture and try tweaking it back to stochiometric (50% duty cycle) if its lean.

stevenstevensteven · #14 08-01-2009, 12:30 AM

In searching through various discussions in this forum I did find this interesting quote from Stevebfl, which addresses my now-very-low CO%, which is certainly below the 0.2% CO referred to in Steve's post, quoted below.

Quote:

Originally Posted by stevebfl

In the last test I mentioned, the concept is to run the car and evaluate the mixture by seeing how it affects the O2 sensor voltage. The sensor is a 0 to 1v voltage generator. It creats voltage that is related to engine mixture within a small range.

Its very likely that the sensor is fouled, but the way to tell is to run the motor (the sensor has to get hot which requires time and engine speed - don't be in a hurry), while monitoring the voltage (sensor on its own not connected). As I stated its likely to be either 1v or zero volts. If its one volt and its working then the mixture is greater than 1% CO (if measured before cat with an exhaust gas analyser - which you really can't do anyway). Here is why I suggested to do the 12v thru Cap'n mixture change. This will lean the car out and unless your are very rich it will bring the mixture through the range 0-0v - 1.0v. if not you can lean it out till it does.

Remember a proper working O2 sensor measures mixture from 0% CO to 1% CO. This is a very small range. The car will start running poorly above 6% CO and below 0.2% CO (maybe higher). The car will be held to mixtures in the range of .3% CO to .7% CO by a functioning system and it can only correct a rich car running less than 4% CO.

If everything is functioning you will be able to lean out the mixture till the O2 sensor just drops from around 1v. Then you will be able to reconnect the wire and the system will correct mixtures less than .5v by adding fuel (within the 10ma correction range we have already tested) till the mixture becomes richer than .5v at which time the current will reverse and the system lean out till it switches the other way. Once the O2 sensor is hot and everything is adjusted then the .3v to .7v O2 sensor swings will be kept in check by about a 4ma total mixture correction.

If this were a training course this would really be a short story. If you don't understand ask me again.

mbdoc · #15 08-03-2009, 09:33 AM

Looks like the catalyst isn't working to reduce NOx

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