91 Acura Integra - High NOx - Failed emissions test - NJ

My 91 acura Integra LS failed the emission test a second time for high
NOx. Could the gurus please provide some input on what I should be
checking? Here are the details.

Test 1:
NOx - 1984
HC - 91
CO% - .34
CO2% - 14.3
O2% - .6

After this test, my mechanic replaced the Catalytic convertor. The
second test results were:
Test 2:
NOx - 1367
HC - 10
CO% - 0.00
CO2% - 13.2
O2% - .9

So, the NOx did drop but not enough to pass the test. (The pass level
of NOx in NJ is 1088)

Any recommendations on what could be the big culprit?

Thanks in advance.

 

wrote in

If you have an automatic, check the EGR system.

Check base ignition timing. With the Service Check Connector shorted, the
timing mark on the timing belt cover should be in the middle of the group
of three on the crank pulley.

I'm wondering if the reduction side of your "new" cat is defective. Your
CO2 reading is WAY too low. It should be well over 15%.

By the way, NJ is *extremely* generous with their limits. Where I live,
they're postively totalitarian about it:
http://www.tegger.com/hondafaq/misc/91_integra_emissions.html

 

indeed. the op needs to make sure the ignition is set correctly too. a
lot of non-honda mechanics don't bother with the service connector when
setting timing and it's frequently out.

 

Thanks guys. Tegger, jim you were right on the mark. It was the base
ignition timing. I had that adjusted and the NOx dropped to 1013 and
passed the test.