1983 380 sl failed ca smog, help please

[deportes]

Two years have come and gone now it failed the California smog test on Hi NO.

!983 380 sl no EGR!

test results are:
15mph 1403 rpm 25 mph 1255rpm
CO2% 14.4 14.40
O2% 0.18 0.12
HC 103 max 124 62 max 68
CO% 0.30 max 0.91 0.18 max0.71
NO ppm 1306 max 886 fail 1142 max 638

After driving home from work 1o miles at freeway 65plus mph took the car in and they let it idle for a few minutes and tested it. 75 degrees temp outside.

Any ideas on what I can adjust to improve the NO numbers.

Thanks.

The smog test place has a shop next to it that they can diagnose and repair/adjust test the car for 250.00 pass or don't pay. It is starting to sound as a simple option.

[Duke2.6]

There may be nothing wrong with your car. The problem is that CA keeps reducing the cut points - an issue I have taken up with my state legislators and the BAR, but I just get the runaround.

There is no specific NOx control device for your engine. It is all built into the spark advance map, stoichiometric A/F ratio, and three way catalyst.

One way to reduce NOx is to retard the spark advance map. This will reduce peak fame temperature where NOx is formed and increase EGT to make the catalyst hotter and more effective. If the cat is working at peak effectiveness the measured O2 content should be zero.

I can tell you how I do this on my '88, but I'm not sure if your car has all the same systems. On my car the initial timing is not adjustable so I:

1. Block the vacuum advance line to the EZL ignition module

2. Use a short piece of wire to short the R16/1 resistor socket

This considerably cuts the spark advance at low engine speed and moderate load resulting in so little engine torque below 2000 the car will barely get out of it's own way, but it significantly reduces both HC and NOx, and my tests read zero O2.

Search under my handle the words - R16/1 resistor- as I have made numerous posts over the past ten years about how emissions are created and controlled and how to make KE systems pass when there are no specific indicated faults in any system or component.

I did emission control research for GM early in my career, so I know the ropes.

Duke

[TnBob]

I thought Calif cars 25 yrs and older were exempt ?? When did they change that ?

Soo glad I left that swamp.

[mbdoc]

The 1984 380SL does have adjustable timing.
.

[deportes]

It's a 1983 and I do not see a EGR valve. Adjustable timing meaning loosening the bolt holding the dist and retarding it a little to lower NO?

Thanks for the replies.

[Duke2.6]

If you can retard the initial timing that will help. Find the emission/tuneup sticker in the engine compartment. It will list the initial timing or perhaps a range. Last time I checked - and it's been awhile - if the intial is one specified number, you are allowed up to 3 deg. advance and unlimited retard. If a range is specified you cannot exceed the maximum, but I'm not sure about retard.

I don't know the details or your systems, but the vacuum advance should be easy to plug with a slug of silicone.

If the centrifugal is old fashioned flyweights and springs don't worry about it. If it has an EZL system like my '88 you can slow the centrifugal by shorting the R16/1 resistor socket as I previously described.

The more information you can tell us about the various systems the better advice we can give.

Duke

[davidlee]

My friend lives down in San Diego and he has a 84 380sel that has the same problem Hi NoX. He goes down to the local Home Depot and buys a qt. of Xylol // Xylene from the paint section and dumps it into his fuel tank at about 1/4 tank and then runs it through and it passes.
He has done it for about 6 years and claims it has not damaged anything.
I dont know what it could even damage anyway?
My friend tried it also here in Oregon on a 91 Honda Civic that had a JDM DOHC Vtec motor installed with Cat and EGR that he couldn't get to pass. It worked for him too.

[deportes]

Thanks, I retarded the timing and enriched the air/fuel mixture and it didn't pass. Afterwards the technician that a day prior had offered to work on the car and charge me 250.00 guaranteed to pass or no charge, went up to 400 due to him thinking that it may need a new catalytic converter.

During my lunch hour I went to a smog repair/test shop and showed the tech / shop owner the results and asked for a estimate, he couldn't give me a estimate but looking at the readings thought that he could test the cat and that a new universal cat would be approx 150.00 plus installation.

Now i am thinking of lifting the car and looking at how many cats are on the car and replacing them for 100 + - each. Then retest.

I was looking at a video where the mechanic takes the cat out of the car and soaks it in gasoline to remove the carbon plugging the pores of the catalyst.
he also recommends running a gallon of paint thinner to help clean the cat, that sounds similar to the xylene deal.

Thanks.

[deportes]

Updating the thread, decided to have the smog shop replace the original 200kmiles catalytic converter and test the car. passed with flying colors. new cat and o2 sensor plus smog test/certificate 425.00 not bad. should last a few years.

[disley]

Thanks for coming back and letting us know how you fixed your problem.