[sauerkraut83]

I have an '83 380SEC (US) that refuses to pass smog, and I could really use some help.

In short, the Mercedes originally failed the smog test for high HC and CO levels. Since then, I have replaced the air filter, spark plugs and the O2 Sensor and now the HC and CO levels pass, but the NOX level fails.

I was recommended to double check the timing and clean out the EGR Valve/Pipe.

Unfortunately, I can't see an EGR on my Mercedes. I've looked throughout the engine compartment (between the exhaust and intake manifolds) and I just don't see an EGR?!

Anyone with a copy of the engine diagram, and what are my other options if I don't have an EGR?!

I really don't want to replace the Catalytic Converter unless I have exhausted all other options, no pun intended.

Thanks for your help.

 

[Aspect]

It's not likely the catalytic converter. High NOx levels are usually caused by higher combustion chamber temperatures. A faulty EGR system is one possibility. A common cause for a malfunctioning EGR system is an occlusion in the end of the tube where it enters the lower intake chamber. It can also be caused by incorrect ignition timing or a lean fuel supply. I'm assuming the car runs well otherwise(no vacuum leaks, no loss of power at highway speed). An expert could probably say more about the subject.

The picture shows an EGR valve on an 84 380 EURO car. The diagram is generic for V8's.

 

[JW560sec]

Welcome to the w126 forum. I believe there are already threads discussing this matter.
i learned last year that not all 380's have EGR system in emission controls. Don't you have a vacuum diagram sticker under your hood? You should use the search function, and you will find lots of info.

As Aspect mentioned, it could be a lean mixture, ignition timing, vacuum leaks, catallytic converter, and really lots of other or combined things. When was the last time you had a tune up? Changed your oil? Does your 380 use alot of oil?

 

[sauerkraut83]

It's not likely the catalytic converter. High NOx levels are usually caused by higher combustion chamber temperatures. A faulty EGR system is one possibility. A common cause for a malfunctioning EGR system is an occlusion in the end of the tube where it enters the lower intake chamber. It can also be caused by incorrect ignition timing or a lean fuel supply. I'm assuming the car runs well otherwise(no vacuum leaks, no loss of power at highway speed). An expert could probably say more about the subject.

The picture shows an EGR valve on an 84 380 EURO car. The diagram is generic for V8's.

Aspect,

Thanks for the picture and diagram, that helps.

I've confirmed, I definitely don't have an EGR. I will look into the ignition timing and fuel supply. The car runs well otherwise, no vacuum leaks and no loss of power at highway speed.

However, after I replaced the spark plugs and oxygen sensor the Mercedes will sometimes stall when idling, but starts right back up again every time.

 

[sauerkraut83]

Welcome to the w126 forum. I believe there are already threads discussing this matter.
i learned last year that not all 380's have EGR system in emission controls. Don't you have a vacuum diagram sticker under your hood? You should use the search function, and you will find lots of info.

As Aspect mentioned, it could be a lean mixture, ignition timing, vacuum leaks, catallytic converter, and really lots of other or combined things. When was the last time you had a tune up? Changed your oil? Does your 380 use alot of oil?

JW560sec,

Thanks for your feedback, sorry for being such a novice, I just inherited this car from my Father.

It is confirmed based on Aspect's diagram and photo, I have one of the 380's without and EGR system. I'm not sure if that's a good thing or not. Its a California US model, which I've heard were not the best 380 models in terms of power, so maybe not having an EGR system helps performance at the cost of higher emissions?

FYI, the Mercedes recently had the oil changed and a few basics (new air filter, spark plugs). I also replaced the O2 Sensor and rebuilt the Power Steering Pump (two broken seals). It doesn't use a lot of oil, although it does have some very small leaks, based on my garage floor.

I am basically just trying to get it to pass smog at this point so I can renew the registrations.

Is there anything else affordable I can do for a basic tune-up? This is the recommended list from AutohausAZ:

REPLACED 10/2010- Mercedes Spark Plugs -
- Mercedes Spark Plug Wires (Ignition Wire Set) -
- Mercedes Distributor Cap -
- Mercedes Distributor Rotor -
REPLACED 10/2010- Mercedes Oxygen Sensor (O2 Sensor) -
REPLACED 7/2010- Mercedes Oil Filter -
REPLACED 10/2010- Mercedes Air Filter -
- Mercedes PCV Breather Filter -
- Mercedes Fuel Filter -
- Mercedes Transmission Filter -
- Mercedes Vacuum Hoses -
- Mercedes Temperature Sensors - (HAS A BROKEN WIRE TO COOLANT TEMP SENSOR according to the mechanic 10/2009)
- Mercedes Lubricants -
- Mercedes Coolant Hoses -
REPLACED 10/2009- Mercedes Belts -

Per your recommendation, I did read into all the EGR threads and a couple of other recommendations were:

- Adjust/Reset the CO
- Check the Pre-Cat and Catalytic Converter for clogging using a thermal test before and after the Catalytic Converter (since the Mercedes was running rich for so long a lot of soot could have built up)
- Adjust/Reset the Timing

I would really like to do all of this work myself, but I feel like it might be time to bring it in to a Mercedes Mechanic.

Thanks for all your input!

 

[garysalas]

fyi and alittle off topic...i noticed you live in ca. you can go to dmv, tell them you failed smog and cali has a program where they pay you/garage 500 dollars to get the problem fixed. you have to go to dmv designated garage. dmv has the paperwork.

 

[SHAUNE55]

fyi and alittle off topic...i noticed you live in ca. you can go to dmv, tell them you failed smog and cali has a program where they pay you/garage 500 dollars to get the problem fixed. you have to go to dmv designated garage. dmv has the paperwork.

What a great idea..it wouldn't work in England though...our government are only interested in taking money off you,if they heard about this scheme they would find a way to turn it upside down so we give them 500!!!

 

[NordRhein]

What a great idea..it wouldn't work in England though...our government are only interested in taking money off you,if they heard about this scheme they would find a way to turn it upside down so we give them 500!!!

---------------------------------
That's not the way it is in Illinois or Missouri. Here you show receipts YOU paid around that and then they will give you a waiver. Better yet Illinois just stopped testing prior to ODB11. California is Nancy Pelousy's state - hope that gives you a clue.

 

[Aspect]

Here you show receipts YOU paid around that and then they will give you a waiver.

I think CA had a similar deal some years ago. I can't say whether or not Pelousy had anything to do with that. To take advantage of the assistance program now you need to qualify as a low income household.