Emmision failure

I have a 1985 MBZ (euro) 280SL and it just failed the Delaware Emmision test at idle. They test at 2500-rpm and at idle and it passed at the 2500 mark.
The readings at IDLE were as follows:
HCC- - - - - -273 (limit is 220)
C0%- - - - - -3.27 (limit is 1.20)

This is a 6-cyl DOHC engine and I do not know where to start looking. Did any of these engines get imported into the USA in other bodied cars?
Are there any English manuals available on this engine?
Got any ideas where I should start?
Yes, I have mechanical skills, but do not make a habit of tearing anything apart without any knowledge.
George F.

[sixto]

The M110 with K-Jetronic was available in the US in the 76-80 280SE and the 77-81 280E. Haynes has a manual for the 280E. From what I've read, the US spec M110s are a far cry from the Euro spec M110s.

Good luck.

Sixto
91 300SE
87 300SDL

[mbdoc]

Here in GA we also have that test. The car must have a very good catalyst & the fuel system adjusted just right for one of these cars to pass.
I had a 1982 280E & was able to get an exemption due to the fact that the car wasn't designed to meet USA specs. Try calling MB in Montvale NJ

[MikeTangas]

Do they test the 2500rpm first, then idle?

If so, you might need a new O2 sensor. Even though not registering as bad, an older sensor won't allow the system to normalize when dropping to low idle from high as quick as it should.

[engatwork]

MB Doc - there are no test in Ga once you get away from the metro Atl area.

[kerry]

Make sure you change the oil immediately before taking the test. In two instances I have taken a failed vehicle home, changed the oil, taken it back and it passed. Also make sure it has a clean air filter.

[mbdoc]

No offense but the 14 counties around IS Georgia, as 75% of the population is here. The rest is south Georgia & Savannah.

Just kidding!!

I have had a lot of trouble getting petrol fueled engines to pass. Here in AZ, all 1967-1996 cars have to pass emmissions. What I normally do is to change the plugs, put in a brand new air filter, and step up the idle speed considerably from factory specs (usually 1200-1400 RPM). Sometimes the DEQ can grant you a waiver, since this is car was not made for the USA, but sometimes not.

Hope this helps...the alternative is a diesel benz...they never fail smog tests.