Big E

The S has now failed MD emissions twice, for HC and NOx levels being too high. After the first failure, we dorked around a little bit, found a vacuum leak, fixed that (though we really should do all the vac hoses), and tried again, only to do even worse on the test.

MD law requires you spend $450 to try and fix it, and since the first retry we spent exactly $0 on it, obviously we didn't satisfy that. So we took it to a local shop (Ralph's in Reistertown, fyi), and he is now suggesting that it *could* be either the injectors or the cat, but is saying that it's possible that the car might never pass. This doesn't make any sense to me. He says it's running very rich. O2 sensor was replaced about 10-15k ago, plugs and wires about the same time.

The top end of the engine is practically brand new, since a previous-previous owner neglected either the t-belt or the cam tensioner and has receipts for 16 new valves and 2 new cams (!). The car idles a little lumpy, which might be motor mounts, and it hunts a little at idle when it's cold, but seems to for the most part run well other than that. It survived 2 autocrosses and a track day, so it can't be too far off.

Any suggestions? Definitely not going to let him do the cat, since he wants $1200 for it, price for the new injectors was pretty reasonable at $160/inj + $200 to install (injectors @ Paragon are $150.) Ordinarly I'd do them myself, but time is short right now.

my87944s

Im not sure what direction to send you... Did he actually put the car on a wide band air/fuel meter to see its running rich, or was that just his opinion?
I would also look at an aftermarket cat. Unless the smog center you are going to is extremely strict, they wont say anything about replacing the cat with an aftermarket part.
I had a car recently fail smog here in CA. for not having a gas cap that sealed properly... I never had any problems with it, but they now take it off, put it on a vacuum tester and test its vacuum holding ability. After I failed, the smog tech pulled one off another car, tested it again and sent me on my way... I felt sooooooo special that day!

Steve PH

Is the Lambda sensor/probe thing doing its job properly ? Suprised the garage owner didnt mention this part of the system ? I think you need to find a specialist who knows emisions by the sound of it !

Big E

Unfortunately I'm getting all the info 2nd hand, since my dad actually took it into the shop and has been dealing with them (we basically co-own the car).

I think he did use a wide-band to determine it was running rich. I asked my dad if the shop had an exhaust gas analyzer, and he said that they had something sorta similar that allowed him to get a feel for what it was doing. So I'm guessing (hoping) that this is a wideband.

Yes, definitely plan on doing aftermarket cat.

The shop has supposedly looked at several things and determined they were fine, I'm assuming the O2 (Lambda) sensor is on that list.

brad-cam

A few other things to check :

- Air flow meter
- Get your fuel injectors professionally cleaned ($50 for all 4)
- Engine temperature (ie. cooling system). A high NOx level can also be caused by the engine running too hot.
- DME temperature sensor - if it's not working properly, the DME will fail to a rich setting

bader$

What were all the readings? HC CO NOx co2 and o2 which kind of test. I very well could be the cat or injectors. My daughters car failed nox and I just cleaned the injectors ( I put a cat on it last year) If you will post the numbers I will try to guide you.

bader$

It's not rich, if it were it would not fail NOx. Nox is a result of high combustion temps and is a natural result of leaner mixtures of fuel injected cars thus the need for some to have an egr valve(ours doesn't) and a cat. NOx can increase with lean mixtures, High Ignition timing and high engine temps. If everything else is right it's just a cat.

Tom M'Guinn

If it's hunting for idle, and idling poorly, and if you did not go through all the hoses, then my guess is that is still has vacuum leak issues. What is the vacuum at idle?

Big E

Unfortunately all the forms from the test are safely in the car I keep going back to the fact that since it failed on both NOx and HC, since they go down in opposite directions of stoichiometric (ooh, finally got to use that word!), that the cat is the culprit. But, then I wonder why didn't it also fail CO too ?

Matt H

Doesnt matter what his opinion is, if the HC are too high the car is running rich. HC = unburned fuel.

Might be scienfically correct but it is practically 100% wrong. High HC will ruin a cat and it can also cause high NOx. Tom is correct, if it is hunting for an idle it still has a problem.
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bader$

HC can also from a misfire which can be caused by a lean or rich mixture as well as secondary ignition problems. The combination of high HC and NOx leads more toward lean misfire, timing or just a bad cat. You can have 2-300 ppm of HC and nothing wrong with the engine of fuel and the cat just not working. It is hard to determine why a car fails with out all the readings

Tom M'Guinn

A guy walks into a doctor's office with an arrow in his chest. The guy complains to the doctor about coughing up blood and a stabbing pain in his chest. What could it be....what could it be...???

Fix the idle.

Jfrahm

Well if it is running rich the O2 sensor is probably gone, and maybe the cat as well as a result. You might have a fuel system problem (leaking injector, bad FPR or damper, etc.) It's easy enough to test the O2 sensor:

http://www.unofficialbmw.com/all/eng..._o2sensor.html

If it seems OK but shows rich maybe you have a fuel system problem but have not killed the O2 sensor yet. A peek at the plugs would also be interesting.

If your injectors are not OK you should be able to have them serviced and/or get some used ones pretty cheaply.

-Joel.

jonnybgood

When the Fuel Pressure Regulator fails it fails to full pressure. Mine failed progresively until the car would not run. Replaced it and it passed California emission the next day. I don't know about high NOX readings but high HC is too rich.

Also as Brad suggested the DME temp sensor when it fails causes an overly rich mixture due to the DME thinking the engine is cold. There are two temperature sensors, one for the insturments (has two spade lug connectors) and one for the DME (directly under the coolant input).