Failed Smog-Suggestions?

Hoss Ghoul · 01:48 PM

Well, the car is running very well, but when I took it to pass Ca smog it failed.

Here's the data:

15mph: 02 0.36 HC 7(meas)/31(ave) CO% 0.02(meas)/0.10(ave) NO 1278(meas)/278(ave)

I failed the NO the limit is 807

25mph: 02 0.14 HC 6(meas)/20(ave) CO%0.07(meas)/0.09(ave) NO 743(meas)/199(ave)

barely passed the NO here, the limit is 746

The NOX is the problem, the other numbers seem nice and low, easily within the limits.

Anyone have a comparison or similar numbers...what should I be looking at replacing?

O2 Sensor? EGR? Cat? I have an appt. with a local Porsche shop, but I'd like to know what kind of hit I'm likely to take. Thus far aside from an alignment and tires, it's been home mechanic time, is it time to pull out the ole credit card, lol...

Thanks guys.

cruzermusic · 09-29-2005, 04:37 PM

i had a new cat. put in 2 years ago and it passed,, this last time the tech. ran it after 3 tries. for 15 minutes to heat up the cat... send your car in after a good long hard drive ,get the motor running tight like you just ran away from your prom dates dad...it might pass...

cruzermusic · 09-29-2005, 04:41 PM

whats your local?hoss .... more chickins in the barn keeps the rooster from pokin..

nynor · 09-29-2005, 05:56 PM

i have the same problem with my NOx. cannot pass at 15 or 25. mine is much higher actually.

nynor · 09-29-2005, 05:59 PM

holy cow... i wonder if my timing and/or mixture has been adjusted at the DME by PO, which is causing my car to fail and to knock (see previous posts, car bucks under boost, but is getting better).

Hoss Ghoul · 09:07 PM

Quote:

Originally posted by cruzermusic
whats your local?hoss .... more chickins in the barn keeps the rooster from pokin..

East Bay, Ca.

I'm going to try the FQS switch and see if I can get lucky.

Assuming that works though, what else am I avoiding by going that route? The car seems to run fine....should I replace the o2 sensor, plugs and wires, etc? I figure a cat will be in order for the future. Am I avoiding a problem that really needs to be fixed, one that ignores a poor tuning condition?

More advice please, thanks.

Porsche944 · 09-30-2005, 05:43 AM

High NoX is caused by high combustion chamber temperatures. The higher temps cause Nitrogen to combine with excess Oxygen. The biggest clue is your CO% (Carbonmonoxide) is low. The spec that Porsche recommends is 0.06%.

This is an indication that the engine is running lean.

The easiest way to "tweak" this is to disconnect the O2 sensor and "back probe" the connector at the O2 sensor lead with a Digital Volt Meter. Set the meter to read the 2 volt DC scale. Start the engine and let it come up to temperature. As the sensor heats up you should see the meter display something between 0.45 volts and 1 volt . Using a 6mm Allen wrench, turn the by-pass on the Air Flow Meter in (Clock-wise) in 1/4 turn increments. Let the meter steady out between "tweaks." Try to get the meter to read between 0.6 and 0.7 volts.

If this seems too complicated, have the inspector do the test with the car in 1st gear. This will get the REVs up and put more load on the engine which reduces the influence of the AFM by-pass.

hpaulb · 09-30-2005, 06:28 AM

Should that measurement be with the O2 sensor disconected or in line.

Porsche944 · 09-30-2005, 06:50 AM

As per the 944 Work Shop Manual, CO adjustment is done with the O2 snsnor DISCONNECTED and the engine at normal operating temperature.

Hoss Ghoul · 11-13-2005, 01:41 PM

I took the car in to an independent Porsche mechanic and he checked/adjusted the timing and suggested a new cat. I ran some fuel injector cleaner and took the car for a free test only. Still failed the NOX, similar numbers...smog tech suggested a new O2 sensor.

In the meantime I've been taking care of a few other issues on the car, installed new rear drums, rear 6x9 box, front 4x6, etc.

Now I'm about to pull the DME and adjust the FQS and give it one more try at passing smog before getting into more expensive solutions(02/Cat/etc)....my thought was this though, and perhaps you could chime in FR Wilk?

If the car is running lean why not go for FQS position 5 or 7? Too much? I know I'm looking for a silver bullet here, but I want to have the best shot possible at getting through the test this time, and before dropping any more cash.

Thanks, I'll let folks know how it all turns out.

Hoss Ghoul · 11-13-2005, 02:38 PM

What direction should the "top" of the triangle(from where it started) be facing when I have the FQS in the number 4 position? I have it essentially opposite, or upside down from where it started. Is this correct?

/\ now \/

Thanks.

nynor · 11-14-2005, 06:16 AM

go counterclockwise all the way, this is 0. turn clockwise 4 clicks, this is position 4.

Porsche944 · 11-14-2005, 07:12 AM

Quote:

Originally posted by nynor
go counterclockwise all the way, this is 0. turn clockwise 4 clicks, this is position 4.

Unless you are using some really shi@@y gas, leave the FQS fully counter-clockwise. This is the "stock" setting for US spec cars.

In this configuration the DME is using fuel and ignition maps that are specifically designed to give optimum performance with minimum emissions with US grade fuels.

If you are still having high NoX readings, then start looking for intake/vacuum leaks. Check the color of your spark plugs!!!! A bad CAT WILL NOT cause high NoX, and neither will a bad O2 sensor. Your "technicians" are brain dead.

If the O2 sensor was bad, the DME would be using a rich mixture to protect the engine from detonation (knock/ping) that could be caused by running lean. If the CAT was bad, (clogged), the engine would run like crap due to the increased back pressure.

nynor · 11-14-2005, 08:25 AM

mine had high NOx. turned out that the cat had been gutted. replaced cat, problem solved. basically, with less back pressure, it allows more air through the system, effectively creating a lean mixture.

Hoss Ghoul · 11-15-2005, 11:28 PM

OK, well I replaced all of the spark plugs today, they looked pretty old, definetly missing material and a little yellowed.

I also adjusted the FQS to what I believe is position 4, it's hard to be 100% sure since the "clicks" are not very distinctive.

I took the car out, filled it up with 91 and drove it around for about 20 minutes. It definetly seems down on power and smoothness, which I am attributing to the ignition timing being retarded.

Hopefully the combination of the new plugs and the timing change will be enough to squeak it through, if not it's on to O2 sensor and the cat.

Hoss Ghoul · 11-17-2005, 11:40 AM

Well I just got back from the testing station, failed again, but damn it was close.

15MPH O2 0.5 HC 24 CO 0.06 NO 787(limit 807)-PASS
25MPH O2 0.2 HC 9 CO 0.01 NO 784(limit746)-Fail

How close is that? Damn. Should I keep tweaking on it, perhaps a bottle of gauranteed to pass or other additive? It's looking more and more like I need to do a Cat...anyone got ideas or a link to an affordable cat?

Thanks.

nynor · 11-17-2005, 12:03 PM

i bet you can find one on ebay for cheap. i bet a muffler shop would weld on one of those high flow aftermarket cats for pretty cheap.

Hoss Ghoul · 11-17-2005, 12:34 PM

I got a quote for 250 at the local muffler shop for just the Cat replacment, 350 for cat and full cat-back exhaust, not including parts.

I'd like an OEM piece since it includes the resonator on the cat. I saw a link on here a while back for OEM fit for $150, can't seem to find it now.

Hoss Ghoul · 11-17-2005, 12:44 PM

http://www.discountconverter.com/converters/display_table.cfm

What do you think?

nynor · 11-17-2005, 02:18 PM

that quote seems awfully high. buy a high flow cat with the proper diamater pipes and length, have them cut out the old converter and weld to your existing pipes. ~175 for the cat, <100 labor.