Nox is caused by high combustion chamber temperatures, in this environment Nitrogen is fused with Oxygen.

Is your EGR system working? When exhaust is recirculated into the intake combustion chamber temps drop.

There may be timing / fuel mixture causing high temps, have a look around the net for a emissions curve that shows fuel mix vs CO , CO2 , HC and Nox to get some idea what is going on.

EGR was checked by a mechanic & by myself & it opens.
I did find a cracked red ruv=bber hose connecting it to the egr vac line.
I replaced that.

I have some old rubber hoses leading to intake I will be switching for new ones.

The engine does run hot 90C.

I have to call around to see what smog repair shops will be able to diagnosis a 30 yo car.

I'm getting a temp gun.
What kind of operating temps of various componemts should I detect?
Can this help w detecting problems?

NOx seems to be a tricky one for the emissions to handle.

Thanks

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83 500 SEC Euro 198K

It needs to open and flow exhaust into the intake. On most cars, manually opening the EGR at idle should stall the motor ( or at least make it run very rough ) If not there isn't enough flow.


Also make sure the EGR opens by vacuum when it should, ( usually part throttle with the engine loaded, just like distributor vacuum advance )

Engine temp is less of an issue, it is high combustion chamber temp that causes high Nox and something you won't be able to measure.

If this car has a 3 way cat it might be failing resulting in high Nox.


I haven't read these but they should apply.

www.magnaflow.com/07techtips/TechBulletin/TB80013.pdf

www.bearriverconverters.com/data/CatOpp.pdf

I have some instructions...I'll have to try this again.
I dodn't know if I was able to complete the test as the old egr rubber was fused at vac line to egr valve
I was able to re move it with aid of heat from hairdryer



not sure




My guess is cat is old& will try to take its operating temp when I get the temp gun
Good stuff guess hope its a vac leak making it lean, exhaust pipe leak is also a good possibility...do they mean exhaust pipes?
Also have to see what a idle hose is thats sticking out. Some say rement of a old washush sp? heating system.

So a/F ratio...would that also be affected by vacumms? or is it just an adjustment of fuel ratio?

Guessing both.


WSell first thing is to try to change more rubber parts that I can do myself & see what that does.

Also check the EGR line.
I have tubing ordered & could change out the entire line.

Hmmmmmmm it all helps & its best I learn on the car not a tech

Thanks!!!

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83 500 SEC Euro 198K

would a 500 sec 1983 have one?
There is a large black cannister then a small valve near front drivers side I don't know what it is? charcoal ?



tubing on black cannister (charcoal ? )is hard
need about 6mm id tubing.
Don't think this would affect the engine

Would love to know what that small valve connected to yellow vac line is

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83 500 SEC Euro 198K

I faile NOX in 2009
replaced o2 senser ^ then it passed flyin colors with Nox.

Could my O2 senser have failed after 4 years?

Maybe it just doesn't work on the electrical end?
How does it affect the system?
I would assume it has to cut or vary air somehow?

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83 500 SEC Euro 198K

Does a hot EGr tube & valve mean anything?
This is on the engine?



its a euro engine so its different in some ways

The idle control valve is a air slide not electronic ignition as it was changed sometime in the life on the car.
This idle control valve was used on the 450 SL engines...wonder if this is adding to it??? I changed some rubber hoses in that area. Don't know how to get out the hose from the aux air slide valve to intake. May have to remove vlve so will leave that to a tech

Found a cracked hose connected to a valve on back of intake manifold. that is also big tubing I don't have so will have to adress it...

This wouldn't make it run great.
Hoses are hard. Will have to get around to have someone change the hose over the 4 valve ports.

Trying & it does seem to be running smoother

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83 500 SEC Euro 198K

83 seems to list this part. I dodn't know where it would be
I haven't seen it so maybe I don't h ave it?

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83 500 SEC Euro 198K

Took apart most of the rubber hoses
well maybe half of the ones I could get access to.
Started about 7pm & finished after 2AM.



Had a dog of a time getting one hose w spring clamo on.
I just don't have the reach & strength
I did it but oh my aching back.

Found that cracked hose that connects behind intake on pass side.
Will have to fix that.

Time for a run...I slept in late & I'm limping around.

Still got some grease under my nails..

Oh, its not very lady like but I love my car & want to make it better.

Thanks for all the help.

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83 500 SEC Euro 198K