failed emission test three times--advice needed

[samhahn]

hi everyone, sorry to bother you all but i wonder if you can give me some advice on what to do to pass VA emission test.
i have a 1991 535i. it failed the emission test because of nox (around 800). i did the following after the first failure:1. major tuned up; 2. use Chevron 93;3. keep it hot before the test. but it scored the same on nox the second time.
i then replaced the oxygen sensor, and the nox score in the third test increased to 900.
is this the time to replace the cat? or are there other alternatives?
thanks much in advance

[Bill R.]

temps high enough to push you over the edge on nox, Anything that will raise the combustion chamber temp will raise nox, What did they do when they did the major tuneup?

hi everyone, sorry to bother you all but i wonder if you can give me some advice on what to do to pass VA emission test.
i have a 1991 535i. it failed the emission test because of nox (around 800). i did the following after the first failure:1. major tuned up; 2. use Chevron 93;3. keep it hot before the test. but it scored the same on nox the second time.
i then replaced the oxygen sensor, and the nox score in the third test increased to 900.
is this the time to replace the cat? or are there other alternatives?
thanks much in advance

[samhahn]

temps high enough to push you over the edge on nox, Anything that will raise the combustion chamber temp will raise nox, What did they do when they did the major tuneup?

thanks. the tune up include replacing and adjusting the spark plugs, and replacing distributer plus air and fuel filter.

[Adnan]

Hi,

High NOx can also be caused by carbon buildup in the cylinders. Try one of those top-end clean treatments as they also clean out the cat. This is not the DIY stuff but one for which you'll have to take it in to a shop.

Regards,
Adnan

[bjl4776]

can you retard the distributor on the M30? If so, the best way to do it is to drive to the emmissions center, retard the timing about 25 degrees, run it through, and then readjust it before you go home. Your car will barely want to get upto 25mph for the dyno, but it will pass emmisions.

[Tiger]

You can use that "guaranteed to pass emission" bottle sold at auto parts store... it is basically dry gas. Run some fuel injector cleaner by Lubro Moly... Jectron and Venti Sauber to clean your valves.

[samhahn]

thank you all very much for your advice.

[Gayle]

Went through exactly the same problem with emissions. My nox was 1100+. Pass in CA is 700ppm. Second time around my nox score was 500 something.

Did all the same things you did plus a decarbonizer-sludge remover called auto-rx (cause hubby had put stp in it to stop valve noise). I think of auto-rx as "seafoam for the faint of heart" (seaform is the product everyone was raving about that month but the stories scared me too much to go with a shock cleaning product). Read up on all the products people touted and in past threads and picked this one. It is about $25 by mail order only. I don't know that auto-rx is the reason for the big improvement cause I everything at more or less the same time. I would try it before replacing the cat.

http://www.auto-rx.com/

If you go this route, read the website carefully. If you do, there is a discount for reading the directions. LOL I of course, did not see that until after I had placed my order. By the way, the same product can be used for cleaning gunky transmissions.

Here is the link to the thread in which people gave me suggestions.

http://www.bimmer.info/forum/showthread.php?t=12713

You might also want to do the stomp test. Would give you clues about the cat and other possible problems. Stomp test didn't work for me but I have since read someothers can't get the stomp test to work for them unless they go through the steps about 5 times. Would give you clues about the cat and other possible problems.

http://www.bimmer.info/forum/showthr...ght=stomp+test

[632 Regal]

another ideas is to reboot the computer...you did do that didnt you?

[Gayle]

Correct me if I am wrong Jeff, but isn't the reason for rebooting the computer is that the dme has a memory and the memory doesn't adjust that quickly. It could instructing the car to continue with the old fuel air mixture even though conditions have changed as a result of all you have done. And if what I just said is totally in left field, educate me please.