Failed smog for NO

[the_jay]

Some of you may have seen another thread where I failed smog a few months back for HC and CO. I sold the car to somebody and now they failed, except this time its for NO. I looked at my past smog records and it appears NO was only 74 back in February, then it jumped up to below the limit when I passed, and now its near 800. Their mechanic said EGR vacuum solenoid, cats, or 02 sensor. Since I just replaced both 02 sensors that rules that out. So its EGR or cats. I found a decent video for checking the EGR here: http://www.youtube.com/watch?v=p1DNBthuRM0 but the cat is out of my control. I am thinking since the NO got steadily worse it probably is the cat. Any advice here? I'm on the hook because they bought the car 2 days AFTER my smog cert had expired (92 days old when the limit is 90 ).

[J30tChumpCar]

A couple things, someone please correct me if I'm wrong, NOX is associated with high combustion temps, the EGR knocks that down with recycled exhaust back into the combustion chamber, for simplicity if the car is pinging it has high NOX output, did you adjust (advance) the timing? Is the new owner putting in low grade fuel?
Changing either of these may help even if the EGR system is inop.

[the_jay]

How does timing change if no one has ever changed the timing specifically? Does it get loose or work its way out of being properly timed?

[J30tChumpCar]

The timing does not work loose nor "get" out of time, this must not be the issue.

[yodawill2000]

Unless the CAS sensor came loose.
Haven't heard of that on a J though.

[the_jay]

The timing does not work loose nor "get" out of time, this must not be the issue.

Yeah it always seemed strange to hear people recommending the timing when I couldn't see why any normal car user would change it.

Could the timing belt b the cause here if it was too loose/failing? No clue when it was done last.

[yodawill2000]

"No clue when it was done last"
That's a Scary thing !

[the_jay]

Yup. I told the buyer this but it was a risk they were willing to accept.

[J30tChumpCar]

It is not likely the timing belt, is there any way to post the current and past emission results?

[the_jay]

HC and CO were reduced to well below limits by changing out the passenger exhaust manifold gasket and the front two upstream O2 sensors in a previous test. NO levels went from 74 in February to 96 in March, to 245 in April, to 843 this July. The limit is 481.HC was close but not at the limit this test. NO levels were higher at 15mph than 25mph.

[the_jay]

They contacted me back and said it was a cracked vacuum hose. Lol. Couldn't be happier there.

[J30tChumpCar]

Great news