emissions...HELP!

[Mike M]

hi,

i have a '91 525im non-vanos...and i am having tons of trouble trying to pass emissions. my hydrocarbons are still just disgustingly high. so far, i have replaced my 02 sensor, fuel injectors, and changed my spark plugs.

i have a d'sylvia chip in my car as well...could that be causing improper timing? i've thrown out the possibility of a head gasket and MAF malfunction since i would assume i would feel some sort of power loss and obvious symptoms, but there are none.

i had heard that putting HEET in your car before the test could help? anyone heard of this/done it personally?

TIA

[p_gill]

Mike,

High HC?

How may miles on your car?

What is your fuel economy (miles per gallon) like?

What test are you failing? Idle or at speed?

How high is really high?

Do you have the complete report and can you post the results for all of the gases that were measured O2, HC, NOx, CO, CO2

Do you have a miss fire? IF HC (unburned fuel) is high I would suspect a missfire. How old are your plug wires? Cap? Rotor?

It is also possible that the HC are coming from the crankcase through the PCV. When was your last oil change?

And finially don't forget that HC can come from too much valve over lap. Is you valve timing correct and is the valve lash set to the loose side of the spec.

A burnt valve could also cause high HC but you should see this in the compression test. Have you done a compression test?

A link for you viewing enjoyment.

http://www.visi.com/~rhayman/smog_fa...Catalyst%20Out

If you keep after the problem you will find the solution.

Good luck

Paul
89 535 230K (passed emissions with flying colors, wasn't even close, although I was worried when they added NOx to the test because my car has never had its NOx tested in its 15 year life until last month)

[Mike M]

hi,

How may miles on your car? 229,000

What is your fuel economy (miles per gallon) like? i'm getting great gas mileage actually...mid 20's

What test are you failing? Idle or at speed? what is at speed? it is failing mostly at lower speeds if that helps any

How high is really high? the test results aren't with me right now, but i believe that i need to be right around 1...but i'm testing at like almost 2.

Do you have the complete report and can you post the results for all of the gases that were measured O2, HC, NOx, CO, CO2

Do you have a miss fire? IF HC (unburned fuel) is high I would suspect a missfire. How old are your plug wires? Cap? Rotor? how do you know if you're getting a missfire? i have no idea how old my plug wires/cap/rotor are...do you think that would really skew my emission results?

It is also possible that the HC are coming from the crankcase through the PCV. When was your last oil change? i've been meaning to do this actually...but i didn't think that it would play THAT big a role.

And finially don't forget that HC can come from too much valve over lap. Is you valve timing correct and is the valve lash set to the loose side of the spec. on the M50, there were no valve adjustments

A burnt valve could also cause high HC but you should see this in the compression test. Have you done a compression test?
no, i didn't know if it was a DYI job...since i'm about to head back to school and i am sort of low on funds. damn poor college kid.


i'll get the official results and post them for you. thank you so much for your help.

[Mike M]

Do you have the complete report and can you post the results for all of the gases that were measured O2, HC, NOx, CO, CO2

HC
standard = 0.80
actual = 1.90
results = FAIL

CO
standard = 15.0
actual = 8.7
results = PASS

CO2
standard = N/A
readings = 420.8
results = N/A

NOx
standard = N/A
actual = 4.80
results = N/A

thanks again!

[632 Regal]

Mike did you make sure the cats were HOT? Yes fresh oil can play a part in the picture too.

[Mike M]

Mike did you make sure the cats were HOT? Yes fresh oil can play a part in the picture too.

yup...drove around for nearly 30 min. including highway driving

[p_gill]

Numbers make a big difference.............

If it were me. I would change the oil and retest.

However this time I would make sure that the catalytic converter was good and hot. Drive the car hard for at least half an hour prior to getting the test done.

Ask the person at the counter how long it will take to perform the test and make sure that the car will not cool off in that time period.

The key to remember here is that newer cars have the converter closer to the manifold than our cars and it is therefor not as critical to make sure that the car is warm.

If you go to the link that I posted you will see that the difference between a "lit" and "unlit" catalyst is about a factor of 1 to 4 for HC. So your factor of 2 should be no problem if the catalyst was infact not up to operating temperature.

See sections
Taking the Catalyst out of the Picture and Checking the Catalyst

If your first test met the warmup and test immediatly suggestions that I made then a retest will probably fail you again.

If your first test was a 5 minute ride to the test station and an hour wait to be tested then I would suspect that you should pass with flying colors.

YMMV

Good Luck

Paul

[p_gill]

I didn't see your reply in time...........

Ok so the catalyst is good and hot. (make sure that they test it right away)

Assuming good combustion and 15% CO2 Then your Grams per mile numbers become aproximately the folowing.

HC - 670 PPM

CO - .3%

CO2 - 15% (as assumed by me)

NOx - 1680 PPM (this is really high also which makes me suspect that the catalyst wen out prior to testing)

However going to the FAQ and entering your data and the failure mode appears to be false air/vacuum leak.

With this in mind assuming that your m50 is similar to my m30, I can tell you what I have replaced on my car in this area.

- hose connection ICV to intake manifold (cost about $15)

- boot connecting air flow meter to throttle (cost about $20)

- vacuum line connecting manifold to brake booster (cost about $3)

The ICV hose was in terrible shape and replacing it helped a lot.

Good Luck

Paul

[Jeff N.]

...long did the car idle in line before the test? The cat can cool off in line and all that driving around is for naught.

yup...drove around for nearly 30 min. including highway driving

[Mike M]

I didn't see your reply in time...........

Ok so the catalyst is good and hot. (make sure that they test it right away)

Assuming good combustion and 15% CO2 Then your Grams per mile numbers become aproximately the folowing.

HC - 670 PPM

CO - .3%

CO2 - 15% (as assumed by me)

NOx - 1680 PPM (this is really high also which makes me suspect that the catalyst wen out prior to testing)

However going to the FAQ and entering your data and the failure mode appears to be false air/vacuum leak.

With this in mind assuming that your m50 is similar to my m30, I can tell you what I have replaced on my car in this area.

- hose connection ICV to intake manifold (cost about $15)

- boot connecting air flow meter to throttle (cost about $20)

- vacuum line connecting manifold to brake booster (cost about $3)

The ICV hose was in terrible shape and replacing it helped a lot.

Good Luck


Paul

you know, now that you mention it, my idle is a bit high at startup (~1000 rpm or above). maybe that hose IS bad. or maybe it's the whole ICV itself, although it usually levels out in a bit. where did you get these parts? just ordered them from BMA or something? thanks so much man. really helped a lot.