Smog check caught up with me

[glenmore]

I have a 1991 300CE with about 150m and I've put up with a rattling cat over the past several years. At each successive smog test, I'd make sure the engine was good and hot and kept my fingers crossed. Since the rattling started, I think I passed 2 tests (every 2 years) but now finally failed one and here are the results:

-----------CO2-----O2------HC max/meas-----CO max/meas-------NO max/meas
15mph----14.50----.07---------106/18----------.70/.04-----------762/1082 failed
25mph---- 14.50---.08----------81/14-----------.57/.02-----------701/1044 failed

From other threads, it looks like could be the EGR valve or most likely a new cat is needed, both expensive.

Any help in narrowing this down?

Thanks,

glenmore
1991 300CE
2000 C280
1990 LS400

[manny]

Based on your numbers, I do NOT believe the cat. conv. is the problem.
Focus on the EGR, as it is mostly responsible for NOx.

[hey_allen]

Yeah, as Manny said, it looks more like an EGR fault. The HC numbers would be affected by a failed cat, whereas NOx is almost entirely the EGR system.

If you got ambitious when you're under the car some time, you might unhook your front section of exhaust, with the cat in it, and shake it upside down, see if anything falls out.
I found a bolt in an old car's exhaust... HOW someone managed to dump a bolt down the front end of the exhaust, I have NO idea, but it had done a good bit of damage to the front end of the cat, bouncing around in there!
I won't say you have one as well, but you may have small chunks of some sort of debris that could be dumped out.

[blueeagle289]

My 300CE would not pass the Smog test in Dallas; had to take it to the Fort Worth Dealer where I bought it and they adjusted the engine so it passed. It was always running well and with full power, but I ran some good injection cleaner directly through the engine and some other stuff thru the air intake and it runs even better. I will certainly look at the EGR system before the next test is due in 08. Ben Carter

[glenmore]

Haven't gotten my car back from the shop but here is the breakdown.

After not passing at a Test Only Station, they alerted me to the Consumer Assistance Program (CAP), funded by all of us California taxpayers. You can get $500 of repair assistance from being Income Eligible or Test-Only Eligible. I qualified under the Test-Only criteria. You send off an application to Sacramento and they spot you $500 for smog repairs IF there is $$$ still in the fund. Lucky for me then that my test was early in the year. You get a long list of approved repair stations that you must select from. I made quite a few calls and they were not encouraging. A lot of the shops were corner gas stations. I got lucky and called a Honda/Acura only shop who then referred me to a nearby shop that sounded good. The shop was neat, filled with cars, AAA approved, ASE everything, and one thing I always like to see, big SnapOn tool chests.

I talked with their smog fellow and he seemed to be familiar with MBZs. Here is what he discovered:

Testing the EGR valve with vacuum showed it leaking/failing. The results of a second smog check showed much worse NO numbers than the original test. No change to the idle so the tube was clogged also. The solenoid switch that activates the valve was also faulty. Total repair about $820. There is a $100 co-pay, so I pay a total of $320. They were able to get parts at reasonable prices, $275 for the valve and $67 for the solenoid and they will just clean the tube.

I initially thought that this program could turn out to be a big boondoggle for all these repair shops to inflate repair costs to "use" up the initial $500 and then keep charging but the guy said that before going ahead they must lay out the repair plan for Sacramento approval, so there is some oversight.

When I mentioned I had recently just replaced the O2 sensor he said that might be a problem particularly if I used generic and just crimped the connections. My repair was OK but he said they have seen problems with generics unless the connections were soldered. He said that these sensors operate at such low voltages that OEM connectors without splices were best followed by a good soldered connection.


glenmore
1991 300CE
2000 C280
1990 LS400

[Strife]

Interesting that you mention that the pros recommend soldering the generic O2 sensor...I was considering this but this area gets so hot I was wondering if the solder might actually melt. Those wires coming off of the sensor are teflon-insulated, by the feel of them. Properly done crimped connections with the right tools and supplies can be as good if not better than solder.

I was also wondering where CA is getting all this money from, considering that its apparently going broke?

[shingleback]

Originally Posted by Strife

Properly done crimped connections with the right tools and supplies can be as good if not better than solder.

Even the best crimped connections are eventually affected by oxidation(and therefore increased resistance). I prefer use solder, shrink tubing and minimize the chances of the joint causing problems in the future.

[Dee8go]

Boy, that sure takes the sting out of forced car repairs.

[david s poole]

based on your numbers your car is running too LEAN.you have too much o2 left after combustion and the co numbers are too low.i have my doubts whether the egr valve in benzes operates at all at those low rpm's.richening up the mixture should make the car pass.

[mr300ce]

Originally Posted by david s poole

based on your numbers your car is running too LEAN.you have too much o2 left after combustion and the co numbers are too low.i have my doubts whether the egr valve in benzes operates at all at those low rpm's.richening up the mixture should make the car pass.

I run a smog repair shop. I participate in the CAP program. His #'s told me the EGR system was the problem. As it turned out, the entire system needed work. His resulting #'s indicate the repairs took care of the problem.

I suggest getting a good aftermarket cat put on, as the 'biscuts' are coming apart inside your cat, and can cause you engine running trouble, bad gas mileage, and overheating if the pieces plug up the outlet.

The EGR system functions under a LOAD condition. It is there to lower the combustion temps to lower the Oxides of Nitrogen gasses. (pollution, Ozone killer stuff, etc). (not to be confused with laughing gas)

The CAP funds are allocated from July-June (state budget). They spend apprx $37 million per yr., which is a drop in the bucket compared to the $10 billion deficit we are running.

You can ONLY qualify upon RENEWAL of your tags, and need a smog test that year...NOT if you are tranfering the title from a sale of the vehicle.

ALL failed cars, reguardless of where the test was done, might qualify for CAP $.

ALL 'Test Only' directed cars qualify. By the way, if you look at the top of the renewal notice you will read that you can go to a Gold Shield station or Test Only station.

I suggest Gold Shield, as they are thoroughly inspected by the state for ASE techs, and honesty.

And, low income people can qualify too.

[Ted Daniels]

Originally Posted by glenmore

I have a 1991 300CE with about 150m and I've put up with a rattling cat over the past several years. At each successive smog test, I'd make sure the engine was good and hot and kept my fingers crossed. Since the rattling started, I think I passed 2 tests (every 2 years) but now finally failed one and here are the results:

-----------CO2-----O2------HC max/meas-----CO max/meas-------NO max/meas
15mph----14.50----.07---------106/18----------.70/.04-----------762/1082 failed
25mph---- 14.50---.08----------81/14-----------.57/.02-----------701/1044 failed

From other threads, it looks like could be the EGR valve or most likely a new cat is needed, both expensive.

Any help in narrowing this down?

Thanks,

glenmore
1991 300CE
2000 C280
1990 LS400

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http://www.pureenergysystems.com/news/2005/03/17/6900069_Acetone/