1985 380SL NOx Emissions
 

The SL failed it's emissions inspection twice. The numbers are as follows:

Emissions /Max
TestLast/First

NOX/3.00 ..........HC/2.00 ..........CO/30.00 ....... CO2/none
3.60/3.95 ........1.16/1.01 ........ 6.47/7.16 .........379/351

It passed the HC,CO, with flying colors but not the NOx. The improvement between the 2 tests was bringing it to my mechanic and he retarded the ignition timing.

Doing some usual work on the car myself I decided with the information available on the forum to try and tackle it and started reading the archives. There I found all the great information on EGR valves and how to clean and check and set to improve NOx.

Unfortunately I can find no EGR valve on this car I have the MB SL CD and find reference to it but nothing inder the hood as far as lines or valves on the exhaust manifolds. All other emissions equip seems to be in place and working the air pump etc. Is this engine before EGR and if it is what can be done to lower NOx? I had read here that 5 degrees retarded will work with the EGR valve operative has anyone had experience in this situation with no valve?

I would appreciate any help as I am between the proverbial rock and hard place.