Failed Nitrogen oxide Emissions
 

My 1987 300E just failed Maryland emmision control. The Nitrogen Oxide was a bit too high. Car had 3.2 where 2.8 is max permisable. Can anyone tell me what I must do to the engine to bring the Nitrogen down to an acceptable level?

Thanks.

Chances are you are running a bit lean -- this means higher combustion temps and hence a little more NOx. I'd say you needed to clean the EGR, but you (thankfully) don't have one.

Check for vac leaks -- at this age, ALL the rubber hoses on the engine are suspect, plan on replacing all of them, including the crankcase ventilation restriction. Don't overlook the idle control valve hoses.

Peter

Thanks Peter

I just did a search and consequently was ready to go out and ream out the tube to my EGR. I'm glad you told me that the car does not have one. I would have been searching for hours trying to find it in the dark.

I'll do that check on the hoses. What must I do to richen up the mixture a tad?

If a vacuum hose is leaking, you're sucking in air, thereby leaning out the mixture.

Replacing a leaking hose would eliminate this problem and therefore "richen" the mixture.