Re: NOx Update (Too Long) (archive)

You have done the most likely thing for NOx. Richen the mixture. As HC and CO go up, the cylinder temp goes down, thus the NOx goes down. This is quite sensitive. Adjusting the AFM as you did, most often solves the problem. It never hurts, though to make sure all else is in order.

Joe

Some may recall my earlier posts about failing NJ emissions for excess NOx in my 86 735i. I received a good deal of help here and have made progress. Not out of woods yet. Here are the results so far. After new tune up items (done @four weeks ago)including plugs, air filter, fuel filter, oil and filter change:

Allowed NOx = 1077; mine = 2408 = FAIL
" " HC = 144; mine = 34 = PASS
CO% = 0.81; mine = .28 = PASS
CO2% = xxxx; mine = 14.0
O2% = xxxx; mine = 0.0
I then changed the plugs from Bosch platinums to standard, switched to cheap 87 octane gasoline and dialed in 3 counterclockwise notches on AFM wheel. Now,

Allowed NOx = 1077; mine = 714 = PASS
" " HC = 144; mine = 103 = PASS
CO% = 0.81; mine = 1.36 = PASS
CO2% = xxxx; mine = 14.0
O2% = xxxx; mine = 0.2

I was able to corral a friend for a few minutes with an analyzer from local BMW dealer's service bay. He put it on Spark plug wire 1 and said its dead...no spark. He put analyzer wire up exhaust and measured something (Temp?) at 136, said it should be about 190-200, noting car had rotten egg smell from exhaust.Then he left, telling me put AFM back one notch (to lean it a little), replace No.1 plug and maybe wire, too.

I replaced the plug even though other was new and noticed that it was wet with gasoline as it came out. New one's in, car runs the same as ever, good with slight roughness at idle and throughout spectrum. I also pulled wire from plug while engne running and it arcs a spark from about 2 inches from plug. Does that rule out bad wire? SHould I try anything else before taking it through emissions again? If only I had an analyzer I wouldn'y have to do all of this blind. TIA.

Follow Ups:

[ Follow Ups ] [ 7-series (E23) Message Board ] [ Msg. Board FAQ ]

Questions, comments, or problems, please visit the Roadfly help desk.