danglerb

Timing is tested, more than a degree or two and you get failed.

Bill Ball

Changing the O2 sensor. I forgot what a chore that is versus when you have an X-pipe.

Bill Ball

Thanks, Thomas. I trust your knowledge of chemistry. I should check cam timing. No way to change ignition timing w/o a Sharktuner.

Bill Ball

IT PASSED!

All I did was fresh gas, O2 sensor, regap spark plugs to correct smaller gap.

.............FIRST TEST.....TODAY
15MPH:
RPM .....1410................1407
CO2.......13.1%.............13.5%
O2...........2.8%...............2.4%
HC.........22PPM.............31PPM
CO.........0.01%...............0.06%
NOX.....869................276 (limit 767)

25MPH:
RPM.......1262.................1265
CO2........13.2%.............13.5%
O2...........2.6%...............2.3%
HC.........20PPM.............18PPM
CO..........0.01%............0.03%
NOX.....922................279 (limit 706)

Note the O2 is only slightly lower. CO is higher but still very low. Could this just be a bad NOX calibration at the first test center (second test was at a different location; same weather)?? If so, it cost me a bunch of wasted effort. Anyway, on to the next task.

danglerb

Congrats, hate this smog testing and have three more in next 5 months, at least one of which should be "entertaining".

borland

One would expect the smog station to have calibrated sensors, but you data makes them questionable. There's only so much O2 in the atmosphere so if NOx goes down, O2, CO, and/or CO2 must go up to balance with what's in the air.

I saw this about cleaning the car's O2 sensor with a propane torch in order to pass smog....

http://www.ehow.com/how_5402396_clea...mog-tests.html

Bill Ball

The old one was pretty clean, at least as far as I could see. Since the only thing that changed significantly was NOX, I'm not sure changing the O2 sensor made any difference.

I spent two weeks fighting with a high NOX failure in my 99 Durango before I figured it out, so I was sitting on pins and needles at the smog facility today worried if I was heading into the same fiasco. With the Durango, I found terrible spark plugs, replaced them and the wires, sure I had found the problem - failed again. So, I ran 3 cans of SeaFoam through the intake trying to do a carbon cleanout and installed new injectors - failed again. Finally, I ordered a new cat, and when the muffler shop cut the old one out, the problem was clear. The old cat was plugged up, enough that the back pressure/reversion was raising combustion temp. New cat and the NOX went from 1900 to nearly zero., and the Durango refound its lost top end power.

So, today when the 928 passed smog with flying colors, it was like I won the lottery or the 49'ers actually reached the Superbowl. I almost did a little dance around the shop, but I restrained myself until I got into the car, then I let out a big cheer. These things can be very frustrating to resolve.

Speedtoys

Or..just replace it.

Yer gonna do it eventually anyhow..