79 450sel failed emissions, help please.

[zeppelinboy]

SO, I have a 79 450sel 4.5L.
It has failed emission twice in the past few days. Both times with hydrocarbons too high.
The limit is 400 ppm @ idle with a max idle of 1350 rpm.
My last test had a score of 432.7 ppm hydrocarbons and .17% CO @ 875 RPM.

Between the first and second test I adjusted the idle hiugher and slightly leaned out the mixture. I bought a timing light @ harbor freight, but it broke within 10 seconds of using it, so I wasn't able to check/adjust the timing.

I am definately having issues with the idle. After adjusting it higher, it will return to a lower idle within a few days. Also, even when I adjust the idle to say 900 in neutral, it will drop to only about 500 in drive. What should the idle be in drive? When it is 500, it runs very rough and lopes along getting ready to die at any second.

Any thoughts on what could be going on here? Any suggestions on squeaking past emmisons.

Thanks in advance for your help!

Justin

[Nutz]

Well,your fuel is not burning completely in the combustion chamber before exiting out the exhaust. Since you don't say where you are from in your profile,I'll assume you are here in the US.Do you have K Jetronic with lambda fitted to your 450 or just K Jetronic basic?

[zeppelinboy]

Sorry for the omission. I am indeed in the US, Colorado to be exact. I guess we tend to forget that the internet includes the rest of the world, especially on this forum.

Anyhow, the car is a US spec '79. I have never looked for an 02 sensor, but I believe that it should have one. Let's assume that I do. I will confirm that when I get out to the car.

Justin

[Nutz]

Look for a frequency valve located near the fuel distributor to determine if you have a lambda.



If so,have you changed it ever? Also if your engine has been running rich for a while,the catalytic convertors honeycomb monolith substrate may be ruined rendering a replacement due to it's inability to perform it's duty by converting CO into CO2.

[OldMercs3]

This is why I bought a '73, no smog testing in Cali.  I could have a coal-fired V16 under the hood for all the C.A.R.B. cares.

[macatron]

In California, 1975 and older gasoline powered vehicles are exempt from smog checks.  Of interest for a lot of M-B enthusiasts, diesels of all model years are exempt.  I'm editing to note that many new diesels (including the new diesel E-class) may not be sold new in California.  When this ban on sales of new diesels begin, I'm not sure...

[zeppelinboy]

So, I have no frequency valve or O2 sensors that I can find.
I did a bit of poking around and have tons o questions, please see my new post:
http://forum.w116.org/mechanicals/emissions-thread-update-name-these-parts/0/

I did however, get a replacement timing light and was able to check the timing.
Timing was advanced 10 degrees at idle with vac. Specs for 79 are TDC at idle, so I set the timing back to spec. The idle smoothed out alot. Not sure how this advance could be causing the high HC readings, but maybe.

Also for good measure I ran some seafoam through and cleaned everything out.

Will go back and redo emissions on monday to see what the changes have netted.

[John Hubertz]

I've always found that priming the test technician with a high-octane bill ($50 or higher), results in fabulous improvements in emissions test performance and often allows a younger, more modern vehicle to experience the thrill of "Being a Mercedes"  and allows Max to avoidmeaningless little moment of government meddling, thus protecting the mercedes dignity and timeliness.

The hypocrisy of a country that has manufactured regional conflicts and wars since world war two essentially as a for-profit business  (with resultant jet exhaust, transportation exhaust, the byproducts of millions of tons of high explosives etc.. ) and then makes a big deal of tailpipe emissions...  gives me the willies.

Ah well...  all I can do is cast my lonely vote for the sociasts - and for "tipping" the emissions guy.

While you are at it you might want to get 50 or so $1 bills... and practice your tipping skills by visiting a local entertainment establishment...  but take your small toolbox as you might find a woman or two who are loose and could use tightening   

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