1987 300E just failed California Emissions Smog Test
 

Hello

I just failed the California Smog emissions test with my 1987 300E

HC and NO were high

see results below


any ideas on where to start, I just changed the plugs, wires, cap and rotor and an oil change before the test

in order of importance , make sure no vacuum leaks, check if egr working, replace o2 sensor if more than 60k miles old, too much carbon buildup ie high compresson for no too high , catalytic converter , compare the last few years of smog checks , I found out they lowered the limits , meaning your car has to run cleaner than new,

thanks for the reply.

Just before the test I replaced the two air idle hoses from the idle valve. Also replaced the hose off the top of the air cleaner housing and the breather hose off the head. Also changed many of the small rubber hose fittings / elbows. I has a slight vacuum leak at the intake manifold and tightened it up and got much better results.

The vehicle does not have an EGR system so it relies heavily on the CAT to reduce NO.

I believe the O2 sensor is 33 plus years old the vehicle has 233 k miles

I have noticed over the years that they have lowered the limits however from 2 years ago to todays test they are the same.

What does a CO2 of 13.3 and 14.3 tell me?

What does a O2 of 1.6 and 1.0 tell me?

attached is the test from two years ago.

Quick way to pass, since your O2 sensor is 33 + years old replace that, then go get yourself a new cat. You should be able to get one for a few hundred dollars. They're relatively inexpensive.

It's been awhile since a CA emission test failure has been reported on a M103 engine, which surprises me. You're registration renewal probably directed you to a "test only" station and either the renewal form or the test report says "high emitter profile."

If the emission system is performing optimally the O2 content should be zero or no more than 0.1 percent, and CO2 should be over 15 percent because all the O2 has been consumed oxidizing HC to H2O and CO2. O2 content is a key piece of diagnostic data. There is a little bit of O2 in the exhaust gas. Plus the converter creates O2 by disassociating NOx to O2 and N2. So if there is no O2 at the tail pipe, the three-way catalyst is working at peak efficiency.

Catalysts "age" with miles and need to be hotter over time to achieve peak efficiency. Also, getting over 200K miles from an O2 sensor is a lot, but they don't last forever. If your 300E was originally sold in CA it should have diagnostics that are not on 49-state models and the "check engine" light should illuminate with a code for an O2 sensor fault, but maybe not in all cases. I believe Mercedes called for replacing the O2 sensor every 60K miles. My '88 190E 2.6 still has the original, but it only has 85K miles.

About ten years ago I did extensive testing on my car due to high HC readings. It passed, but had little HC margin, especially the 15 MPH test. I found information on this site about the R16/1 resistor. It controls the rate of spark advance with engine revs. The OE resistor is 750K. Removing it increases the rate of advance with revs and replacing it with a shorting plug (made out of a short piece of wire with the insulation removed from the ends, formed into a "U" and jammed in the socket) decreases the rate of spark advance with revs.

For normal driving my R16/1 resistor is not installed and for emission testing I install the shorting wire and replace the short molded rubber hose from the inlet manifold nipple to the 3mm nylon tube that goes to the EZL module with a piece of generic 1/8" vacuum tubing that is plugged with silicone. This disables the vacuum advance.

For a given speed and load the less ignition advance, the lower the peak combustion temperature, which lowers "engine out" NOx. At the same time it increases EGT, which will increase catalyst bed temperature

This configuration lowered my HC by about 50 percent and NOx a whopping 90 percent, though NOx was not a problem, and O2 is 0.0% at both speeds, so the catalyst is operating at peak efficiency. The engine is totally doggy below 2000 due to the retarded spark advance, but both tests are below 2000 (2nd and 3rd gear) so the effect is dramatic. I use a "drive though" test station a couple of miles away, but use a 5-mile route to get there so the cat fully warms up. I usually arrive about 0930 and get right into a test bay or maybe wait for one car to be completed, and NEVER SHUT OFF THE ENGINE. In fact I open the windows, turn on the A/C full and keep engine revs at about 1200-1500. This helps keep the catalyst hot.

Assuming you have a free retest you can replace the R16/1 resistor with a shorting plug and plug the vacuum advance as I described above. This will help, but may not be enough to do the job with your aged O2 sensor and catalyst, but it costs nothing out of pocket.

If it still fails I would probably replace the O2 sensor first and then the cat if it still fails, but let's wait and see what the new results are.

I strongly suggest that you search for threads stated by me, Duke2.6, using search words R16/1 resistor, and read those threads to understand how spark timing affects emissions and how to modify the spark advance map by shorting the R16/1 resistor disabling vacuum advance. As you probably know the initial timing is not adjustable - mine is 9 deg. BTDC, but that's okay. Retarding the rate of advance with engine revs and disabling the vacuum advance is more effective and easy to do on these engines.

Back before I learned about the R16/1 resistor, fifth gear was not useable below about 45 MPH - no torque. With it removed I can drop it into fifth at 35 MPH, and it easily pulls from about 1200. Around town fuel economy also improved by nearly 20 percent! The difference may not be as dramatic on an automatic (that I assume your car has), but is probably noticeable.

The R16/1 in my 190 is located on the plastic cover inboard of battery. It's visible and looks like a unconnected electrical connector wrapped up in electrical tape, so it's easy to access, but I remove the battery which takes about a minute to get better working space.

I believe it's in a different location on the W124 chassis - somewhere near the master cylinder, although that might be for the S-class, I'm not sure. More searching on the R16/1 resistor should lead to the location because there was a lot of discussion on this ten or more years ago, but not recently.

BTW, I'm a retired automotive/aerospace engineer - MSME from the U. of Wisconsin Engine Research Center where I did emissions research, so I understand emission creation and control at a very low level of detail.

Keep us posted.

Duke

Interesting info about the resistor. I ran my car with the resistor and monitored more than a dozen fill ups and also did the same thing without the resistor using only 91 octane. Lowest combined city/highway driving with resistor was 15.7 mpg and the highest was 22.3 mpg. Without the restor my lowest was 17.2 mpg and my highest was 24.5 mpg.

Most of my driving is now pretty local - surface streets with round trips of 5-10 miles... almost no freeway driving. I think the reason I got a better improvement in fuel economy is that I can now use fifth gear on typical 35 MPH boulevards.

I don't have to downshift until below about 30 MPH, which is about 1100 revs. Below this I can feel the engine labor and response is sluggish - probably due to lack of sufficient spark advance. Given the torque peak of 4600, the engine is not designed for low rev torque, but it has excellent torque bandwidth with the R16/1 resistor removed from 1500 to the rev limiter.

My engine system engineering requirement for a responsive high performance road engine is 80 percent peak torque at 2000 with a manual trans and 90 percent with an automatic. Back in the nineties I had my car on a chassis dyno, and it actually made 80 percent at 2000, which surprised me because it felt pretty soggy down low. With the R16/1 removed it must make 90 percent at 2000, which is excellent for such a high torque peak engine!

I actually just use 87 PON, and if ambient is below 70 and coolant at the usual 80C it doesn't detonate, even if I drag it down to about 700 in second gear at a stop sign and then go without declutching and going to first. Since I usually only drive it during the cooler months, 87 is okay, and if ambient is over 70 and coolant is over 80C I can "drive around" any slight transient detonation by shifting at higher revs. Usually I shift at 2000-2500.

You've got a 300E, right? Where's the R16/1 resistor located?

Duke

Fantastic info above and beyond the basic "if the HC is too high the engine is running rich, if the NOx is high you need to bring down combustion temps with more fuel or by fixing the EGR" tips.

Saved for future reference.

HI

I was out of town for a while.

Just went through my smog test results going back to 2004 and made a spreadsheet of the results.

There were times in the past that the HC was high but just passes.

It seems like with the latest test all measurements are on the higher side , even the ones that passed. I am going to take some voltage measurements of my O2 sensor with a voltmeter to see how it is functioning.

let me know if you have any comments to my results over the years.

Thanks

When I go through the smog I drive there in first gear to get the cat lava hot and then leave the car running. Seems to work.

then move out of the commie state,I did in 83

I don't see any clear trends over the years. The 2004 test was very good, but then some emissions went up and back down again. This is typical and is probably due to differing test conditions and equipment calibration. Then there was a dramatic increase in emissions from the 2017 test. The high CO and HC indicates a rich mixture, which could be caused by a degraded O2 sensor, or it could just be insufficient catalyst temperature. As catalysts "age" ever higher bed temperature is required to reach peak oxidation and reduction efficiency.

The cat heats up during the 15 MPH test, which loads the engine more than the 25 MPH test, so emissions are usually lower for the 25 MPH test.

You should check O2 sensor function. What's total mileage on the car? It may just be wearing out, but I'd make an even odds bet that if you short the R16/1 resistor socket and plug the vacuum line to the EZL module to disable vacuum advance it will pass. This cut my HC by about 50 percent and cut NOx by a whopping 90 percent!

The reason is that the retarded spark advance reduces flame front temperature below the "knee" where NOx formation dramatically increases. I'm not sure exactly where it is, but a few hundred less than 4500F. The retarded advance also increases EGT, which gets the catalyst hotter, so it more efficiently oxides HC and CO2 and reduces NOx. Again, the key is O2 content. It it's zero or no more than 0.1 percent, the cat is operating at or near peak efficiency, and the "E-part" of the KE system, which includes the O2 sensor is maintaining the ideal stoichiometric mixture.

The emission test station I go to ("test only" type required) is a "drive through", like a car wash, with three bays about two miles from my house, but I take a five mile route to get there to fully warm up the engine and accelerate aggressively - put as much load on the engine as possible to heat up the cat.

I test in February, and arrive about 0930 and usually go right in or am the first in line. I open all the windows, turn the A/C to max and hold revs at about 1500 while waiting, again to keep the cat hot. The more load on the engine the hotter the cat gets.

Never leave the car at a test place and pick it up later. Always go to a place that gets you in quickly and NEVER shut off the engine.

BTW before the end of the 25 MPH test the aux. electric fans switch on which means coolant temperature has reached 105C. Since I usually only drive it during the winter months, they never come on, except during the emission test due to the "special" spark advance map for emission testing. In fact I can't even remember the last time the coolant temp hit 100C, which is the point that the viscous fan clutch tightens, and I hear it "roar" above about 2000 revs.

Duke

Same here but moved back because I like to go snowboarding and hang out on a sunny beach in the same weekend.

Do some research on LA smog in the 60's and get back to us if you still want to live there without emission controls.

Thanks

I'll consider jumping the resistor and plugging the vac line.

I was away out of town for a while.

I just measured the O2 sensor voltage. Started the car it was already warmed up. Voltage measured around 440mV, let it run for a while and reved it a bit and it reading on the digital meter jumped around between 100mV and 700mV

According to what I have read this is the typical behavior.

I was surprised that it jumped around that much at idle and also when I would hold to rpm up around 2k rpm.


I also confirmed that 13.5VDC was going to the heater part of the O2 sensor.

I guess my O2 sensor is fine?

another detail I left out, the smog tech ran the test with the hood up. I believe the hood should stay down, he also put a external fan in front of the radiator, it was only around 70 degrees that day.

Over the years during past tests I recall the temp creeping way up to 105 and above and the fan on. When I looked at the temp gauge when the test was over it was only around 100C.

Sounds like it didn't get hot enough?

The guy I go to always leaves the hood open and places a fan in front of the car to blow out the fumes.

Change the O2 sensor, do an oil change, fill it up 3/4 of a tank with high octane quality fuel and take it for a 30 minute high revving ride, don't turn the engine off and if you have to wait go around the block again. I'm almost certain it will pass.

Both my cars with the same engine passed doing so and both were in really bad shape when I got it smogged.

so to confirm short R16/1 which will yield 12 degrees of retard. I read lots of posts about people removing the resistor and leaving it open which is no retard.

Shorting the R16/1 resistor does not retard maximum advance with engine revs, which is 32 degrees. (Initial timing is fixed at nine degrees and is not adjustable.) It merely slows the rate of advance with engine revs, so maximum advance doesn't occur until higher in the rev range. That means that during emission testing, which is done at fairly low revs, there is less advance, which cools peak combustion temperature for less engine out NOx and the higher EGR heats up the cat bed, which helps an "aged catalyst" operate closer to peak efficiency in both oxidation and reduction modes.

Blocking the vacuum signal line to the EZL MUST also be done in conjunction with shorting the R16/1 resistor socket to minimize advance under emission test conditions in order to yield the lowest recorded emissions.


As I have previously reported, removing the R16/1 resistor creates the most aggressive increase in advance with engine revs, and it allows me to use fifth gear as low as 30 MPH. With the original 750K ohm resistor installed it had so little low end torque that fifth was not useable below 45 MPH. Also, around town fuel economy increased from18-22 to 22-24. It easily keeps up with traffic shifting at 2000-2500 revs.

In your last post where you quoted my last post, I asked for your car's total mileage. I even underlined the question, but you didn't answer. I still want to know.

I hope you searched and read the threads started by me, Duke2.6, to see the testing (advance with revs and cat inlet temperature) and analysis I did over ten years ago with both the OE resistor, no resistor, and shorting the resistor socket.

It sounds like your O2 sensor is okay. Voltage should flip about two times per second at idle speed. As O2 sensors age, response time slows, and that can increase emissions. Again, how many miles does your car have and do you believe that the O2 sensor and catalyst are original???


The Mercedes maintenance schedule for my '88 calls for replacing the O2 sensor every 60K miles. I now have 85K, but have not replaced it because I have no reason to believe the O2 sensor has degraded enough to need replacement.

As far as engine temp and EGT is concerned I can pretty much guarantee that by the end of the test with the R16/1 socket shorted and vacuum advance blocked the aux. electric fan will engage before the end of the tests because coolant temp has hit 105C. That's because the higher EGT throws a lot more heat into the cooling system as it passes through the exhaust ports, and that's necessary with an aged catalyst to get it hot enough to operate at or near peak efficiency.

You will also probably notice that engine response is sluggish around town due to the severely retarded spark advance map. It's very noticeable on my five-speed because I can load up the engine at very low revs. With an automatic it may be less noticeable, because when you load the engine, revs will always jump to at least converter stall speed that I expect is about 2000 revs. You can check by firmly applying the brake and briefly floor the throttle. Revs will freeze at converter stall speed within about a second. If you do the test I'd like to know the result.


Duke

Thanks for the additional info.

The car has 233K miles. I bought it from the original owner in 2001 with 150K miles.

I just spent about an hour reviewing all the records from the original owner. In March of 1997 the car was brought to the dealer with an engine that was very hard to start at times and would die on acceleration at times. They replaced the Ignition Coil and O2 sensor then. March 1997 with 107K miles.

So it looks like the O2 sensor is 22 years old and has 126K miles. That being said I attached a volt meter to it yesterday and it seems to be working fine.

I found the original receipt for the purchase of the vehicle, the original owner paid $38,187.50 for the car on Feb 17, 1987!!!!!!!!



Thanks!!

https://www.bls.gov/data/inflation_calculator.htm

$87,793.95

126K is a pretty good service life for an O2 sensor, so I expect the issue is catalyst aging - but at 233K miles the cat is probably living on borrowed time.

At this point I think you should short the R16/1 socket, block the vacuum advance, and retest. I'll give 50/50 odds that it will pass, and start shopping for a replacement main three-way cat.

I made a shorting plug out of a short piece of 12-gage wire, stripped the ends and folded back the wire strands over the insulation, bent it into a "U" and stick it into the socket. Then I rewrap it in electrical tape, like Mercedes did at the plant. No one will ever know...

To disable the vacuum advance I cut about a 2" piece of generic 1/8" vacuum tubing, plugged it with a slug of silicone sealer and use it to replace the short molded rubber tubing at the inlet manifold end of the vacuum line to the EZL. Most of that vacuum signal line to the EZL is 3mm nylon tubing with molded rubber adaptors at the manifold and EZL ends. I usually install it at the manifold end, but I need to take the air cleaner off. The EZL end will work too, but I guess I'm paranoid enough to not have a non-OE part at that end, which is visible. If attached at the manifold, it can't be seen.

I keep the shorting plug, piece of plugged vacuum tubing, and OE 750K ohm resistor in a small ziplock bag in the glovebox. It takes about ten minutes to make the change, including removing the battery to easily access the R16/1 resistor socket.

Did you find the R16/1 resistor socket on your 300E? On my 190E 2.6 it's visible on the inside battery compartment plastic trim panel secured with a wire tie. I think it's in a different location on both the 124 and 126 models - maybe underneath the master cylinder. Where is it on your 300E?

The inflation adjusted MSRP on your car is interesting. Back then Mercedes' marketing slogan was "engineered like no other car in the world", and I think that was mostly true although they seemed more complicated than necessary. The throttle linkage on the M103 engines is one example.

Then Lexus brings out the LS400 in 1989, which was equivalent to a V-8 S-class for the price of a 300E. It became a whole new ballgame.

Mercedes made a ton of money in the American market that they used in the late eighties to buy into the German aerospace industry. Then the Soviet Union fell, defense spending plummeted, and all that money evaporated.

I'll never buy another Mercedes, but I may want to be buried in my 190E 2.6 special order five-speed instead of a coffin. ;)

BTW, if you pass the test, re-enable vacuum advance, but don't reinstall the original R16/1 resistor. Leave the socket open, and let us know if you feel better around town throttle response/low rev power and better fuel economy.

Duke

Thanks!

So do you think the O2 sensor should be replaced? I just ordered one today and it should be here next week.

If it passes why should I shop for a 3 way cat?

I believe I am burning a good amount of oil. I believe this is contributing to the high HC readings.

The R16/1 resistor is near the master cyl, access is easy. So I remove the resistor and inset the U shaped wire jumper, or leave the resistor in and short the resistor?

From your test results I think the O2 sensor is okay.

My hunch is that the main cat is aged to the point where it no longer operates efficiently enough to pass emissions testing, and high oil consumption certainly accelerates catalyst aging. How many miles per quart is it doing?

I suggest before you start replacing parts, do the temporary R16/1 mod and disable the vacuum advance as I previously described and then retest. Emissions should be much lower, maybe enough to pass. I assume the test station offers one free retest, so this approach costs nothing. If it fails the new test results may help determine if the O2 sensor is bad, the cat, or both.

If it does pass, especially with little margin, then you will be facing similar issues in two years.

Remove the R16/1 resistor and short the connector with a jumper wire as I previously described. Put the resistor in the glove box or a safe place were it won't be lost or damaged.

There have been threads over the years about replacement cats. I don't know if you can buy one from MBZ anymore, but if they are available they will no doubt be very expensive. Generic three-way aftermarket cats can be welded on by exhaust shops, but some reports say they have short life.

After the emission test remove the shorting wire from the R16/1 connector (and enable vacuum advance), but don't reinstall the resistor. I expect you will detect better performance and fuel economy due to the more aggressive spark advance map than with the OE resistor installed.

Duke

Cats from MBZ are no longer available for my vehicle. When they were they were $1800.

I orderd an O2 sensor it will arrive next week. I plan to install it an also get a cat before the next test. I figure the O2 sensor is 22 years old with 126k miles and is most likely covered in soot.

when I got home from work today I connected a voltmeter Fluke DMM to my O2 sensor.

It jumped around from around .100 V to .700 V. I counted the times the meter changed or updated the voltage reading value in a minute and was close to 140 counts.

I always though the life span of a o2 sensor was 50k-60k miles

It's flipping a little more than twice per second or a little under 0.5 Hz. Sounds okay to me. O2 sensor aging can be indicated by slow response time, but flipping a couple of times per second at idle is about what I recall when I tested mine over ten years ago.

On my '84 190E 2.3 there was a dash light "O2 sensor" that switched on at 30K miles to indicate that it needed to be replaced. I asked the dealer how they turned out the light and they said "remove the bulb". So that's what I did and left the O2 sensor alone.

I figured that since O2 sensor technology was fairly new back then Mercedes simply "programmed" a replacement requirement, so they didn't have to replace any on warranty.

When I sold the 2.3 at 50K miles to buy the '88 2.6 it passed emissions with plenty of margin.

The '88 maintenance schedule calls for replacement at 60K miles. Mine now has 85K and appears to be in proper working order.

I'm not sure what the nominal life of an O2 sensor is or what the statistical failure distribution is, but if it's not working properly, it will usually result in high emissions during testing, and those cars with diagnostics will show a "check engine" light and O2 sensor code, if it is not performing properly.

Remember the old adage: "If it works don't fix it."

Duke

I'm glad you FINALLY bought an O2 sensor. Yes, 80-100K is about right. And you have 233K on the ORIGINAL muffler? Magnaflow makes Kaliforniastan approved mufflers. I replaced BOTH of mine on my '97 CL600 with only 67K. My first Benz was an '87 300E. Had little trouble with it and sold it with about 180K. It is still in the area, now has over 300K with the ORIGINAL engine and transmission. Folks, if you take care of them they run forever, well at least a LONG time. Follow the factory recommended maintenance or buy a Toyoter or a Honder!
Anziani
'97 Cl600 69K

No the muffler isn't original. The original owner replaced both the muffler and the resonator and I changed the muffler about 12 years ago. The cat has never been changed. I plan to change the cat with a Walker.

Hi Everyone

Just wanted to pass along an update.

I changed the CAT and the vehicle passed smog today. NO way down, HC is down as well but still a bit high.

Still pan to change the O2 senor, it is super tight, multiple applications of PB blaster, will try to remove in teh next day or two if still tight will have someone take a torch to it.

Thanks to everyone for their input and suggestions.

See attachment for smog test results

A new cat works wonders, and should cover up minor engine issues for awhile.

Did you try heating up the bung for the O2 sensor with a propane torch? It'll kill the sensor, but it's probably close to death already. The heat differential between the bung and the sensor should help fracture the thin layer corrosion in the threads. Once it starts moving, twist the sensor back and forth to grind the chunks of corrosion into dust, so the threads don't get jammed or tear (galling). Install new sensor with careful application of anti-seize on the threads to make removal easier next time.

No didn't apply heat yet, just some PB Blaster. If it doesn't come out next attempt, heat will be applied.

Are California Smog test requirements the same across the state and are they the same for all vehicles that are required to pass a smog test?

I just had my 1996 Mercedes C280 smog'd and my print out showed that my car could not go have a HC reading of higher than 51 at 15 MPH and not higher than 35 at 25 MPH.

However, murphysf's California Smog snippet showed that his car's max HC could have been 110 at 15 MPH and 77 at 35 MPH.

Stevester, you don't say where you are from. As far as I know the smog requirements are State wide and the certificate doesn't refer to MPH but to RPM's. I just pulled my last test on my '97 CL600 with the following results:
Idle HC (max) 100 (Ave) 17 (Measured) 10
2500 RPM (max) 130 (Ave) 12 (Measured) 11
I don't know where you got your numbers or who Murphy is. My hulking 12 cylinder beast passed with flying colors but I do have new O2 sensors and Magnaflow cats that were installed a year ago. But then the car only has less than 70K. However, this is my 5th Benz and I have never had any smog pass problems with any of them, even those over 200K miles.
Anziani

It sounds like you had an acceleration simulation mode (ASM) test, but apparently there are still some areas in CA that just do the old two speed, no load test at idle and 2500 as reported in the previous post.

The ASM test is run at 15 and 25 MPH with more load than is required to maintain those speeds on a level road, and that's why it simulates acceleration.

The cutpoints are based on the year group of the car and the weight, in 50 pound increments, which is computed at curb weight plus about 150 to 200 pounds to account for at least a driver, and the newer the year group, the lower the cutpoints.

The Bureau of Automotive Repair has a single page pdf on their Web site with a formula for computing the cut points, and the variables to plug into the formula for any year group are in a table. This is because certification limits became lower over time. Run the numbers for your car in the proper year group and you should come up with the same cutpoints as on your emission test report.

The ASM test reads proportional emissions in percent and ppm, but the original certification test requirements were based on absolute emissions in grams per mile. Thus for the same engine a heavier car will have lower cutpoints than a lighter car, an example being that the 260E/300E 2.6 will have slightly lower cutpoints than a 190E 2.6 within the same year group.

I have had numerous discussions if not outright arguments with the BAR that there is no way to directly correlate proportional emissions to the absolute certification standards. They have grudgingly agreed, but claim that the cutpoints are based on statistical analysis of their emission test database, and apparently the EPA is okay with that, but it becomes a real issue if you bust a cutpoint by a few ppm.

Duke

I received a letter from the NJ Motor Vehicle commission telling me my 1988 300CE no longer had to be inspected. They instructed me to remove the inspection sticker (which is still there) from the front windshield and carry a copy of the letter in the glove box, which I have done.
Fwiw, I have 153,000 on the Odometer, 112,000 are mine since 2001.;)

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