SharkSkin

Don't go in for the check until you are sure you've burned off any fuel additives you've put in there. Also, at least in Ca., Chevron gas -- which I don't use otherwise -- burns cleaner. My truck failed as a gross polluter and the guys at the smog shop say they can always tell when a vehicle is burning Chevron gas. I don't remember what effect it had on NOx but the HC went from about 30% over the limit to about 20% under. This is on a carbureted truck with no cats(and 320K miles on it! ) YMMV.

khalloudy

Pretty simple i had a NOx issue that drove me and my mechanic crazy. New MAF was all it took... forget rebuilt forget potatoes. If you have no vacuum leaks and you got clean plugs and you ignition is up to par, the 20 year old (or rebuilt) MAF is the culprit. Been there, done that.

Champagne

Ed,

are you sure the O2 sensor is working. I seem to remember you had problems with the length of the wires when you installed your X.
Maybe the wires are rubbing somewhere and shorted out.

Paul

Ed Hughes

Maybe the MAF is bad, but my car is only 16 years old!! I've nothing to lose trying the holistic approach, and stand to save the cost of the new MAF on my workbench.

Paul: I've got the O2 sorted out, but you're right I had the issue of the way the old one had it's wires run. All fixed now.

inactiveuser92616

if you were running pure gasoline when you failed, try running it with E-10 (10% ethanol) it burns cooler so has less NOx. In colorado E-10 is the only stuff available at the pump, but if you were running pure gasoline than the switch would help. Richening the mixture a slight bit would also help the NOx, but at a tradeoff of more CO and THC.

Thats the only real cheap solution. There are other methods to reduce NOx but they are more expensive or complicated, like water injection, airpump with urea SCR, etc.

Ed Hughes

Ahhhhhmmmmmmmm!!! The Force runs strong in my 928, and legal too!!

Went back in this morning, and passed with the high speed NOx down to 363.
This is what I did, of which the cumulative effect worked:

1. Cleaned the MAF with the CRC MAF cleaner.
2. Got a 200 mile chunk out of a tank with a bottle of Techron, most of it at high RPM. Numerous launches from stoplights up to 100 or more.
3. Did Doc's recommended recalibration of the computer.
4. Drove it for 50 miles to a Dr. appt. prior to taking it in for the retest.

So, it is possible to change the outcome of such test results by a good diet, and clean living.

Ahhhhhhhhhhmmmmmmmmmmmmmmmmmm!!

Mike Frye

Ed, I know you mean 1000 (rpms) right?

This just proves that your karma is good. Pay it forward grasshopper. And congrats!

Steve J.

I got better readings at higher RPM's (lower gear). Standard NOx, high speed 25mph=1014ppm. (So Ed, you weren't too far off with 1124ppm. But 363ppm is a lot better! What RPM?) My NOx test results over the last few years for the '87S4:
2003 - 372 ppm @ 1219 RPM, 25mph
2004 - 277 ppm @ 1938 RPM, 25mph
2005 - 263 ppm @ 1865 RPM, 25mph
During the most recent inspection in 2006, they used the sniffer up the tailpipe but did not run the car on the dyno for some reason. Test results printed were 0.00 ppm NOx.

docmirror

aaahhhhhhhhmmmmm,,,,,,,,aaaaahhhhhhhhmmmmmm. Peace brother - all is right with the bwwwahhh. Glad it's fixed, maybe it was just gunky MAF and not hot enough.

AO

Please send all monetary donations via PayPal to:

The928Shrine@yahoo.com

j/k

Ed Hughes

I asked the guy about the R's. He has a max of 2400 for the 25mph test. But, he remembered I had an auto, and said the "state of Texas" specifies the car be in drive. I then told him "Porsche" recommends 2nd, 3rd gear tops. He told me he had to go with the state's mandate....

When we were testing, I showed him how my car in Drive was barely cracking 1000 rpm, and pointed out I didn't think it fair. After it was over, he did put in in 3rd, and I showed him that the R's were up to only 1250 or so, but he said I passed, and left it at that. He said maybe next year he'd try it in 3rd...

Ron_H

Well, thank you DocMirror. Now I know why I get such poor mileage. I disconnect my battery every day after parking the car. The next day I reconnect the battery and drive off. Gremlins lurk therein and the best minds around have been unsuccessful in flushing 'em out. Anyway, the computer is not operating correctly until a suitable readjustment period? Is that the problem? At the price of this crap we burn as fuel it is beginning to be attractive to resume my gremlin chasing and cease disconnecting the battery all the time. If I park for more than two hours I disconnect. (please no lectures on how to use a multimeter, no matter how well intended. we have exhausted the "bad relay" fixes and done Dave's "refurbish the fuse panel" thing. This ***** gremlin is elusive. Several hours in Devek searching for it have left my VISA card supplier rich beyond their wildest imagination and the virus stronger, I'm sure.) So now I shall resume my search prodded on by the ever increasing (daily) increases in fuel prices in Silly-con Valley.

docmirror

No prob. Next time I'm out is Scummyvale I'll be glad to assist with the batt drain. I'm pretty handy with a MM. Another work-around is to add a trickle charger from Pep Boys. Just run a insulated jumper out the grill area to the charge post and a ground and plug it in when you get home.

The characterization period is not really a big problem, but reaize that you're very rich on the mixture for the first 2-60 miles. This can cause secondary issues down the road.