cam69ss
Thanks for your reply, I carefully re-read the inspection report: your are right!
Duke2.6
Thanks for your instructions! I will run more tests as you suggest. So far it looks like my EGR valve is broken.
I wonder whether a broken diaphragm could lead to a vacuum leak that could be responsible for the increased HC as suggested by manny and boneheaddoctor.
Also, I will shorten the R16 resistor (I pulled the 750 Ohm original resistor) to retard ignition.
Then I will make sure the catalyst is hot.
I may also replace the spark plugs and double-check the ignition system.

I hope that will suffice to pass the second test.
Thanks to everyone, Bruno

Hi
I have

- replaced the EGR valve
- resealed the exhaust manifold/downpipe junction (not sure it was necessary)
- shortened the R16 resistor
- disabled ignition vaccum timing advance
- drove the car hard just before the test

and I passed!

Here are the numbers (all in grams per mile)
HC (limit 1.2), 1st test: 0.98, retest: 0.21
CO (limit 20) 1st test: 6.13, retest: 3.62
NOx (limit 2.5), 1st test: 3.01, retest: 1.45
CO2, 1st test: 445.99, retest: 457.01
O2, 1st test: about 0.4%, retest: nd
All values have significantly improved.
Thanks to everyone, especially to Duke!
Have a nice weekend, Bruno

HC - 79 percent reduction
CO - 41 percent reduction
NOx - 52 percent reduction
O2 - 100 percent reduction to zero (It was all being used by the cat, which is what you want)

One thing that is not clear is if you adjusted your duty cycle before or after you replaced the possibly leaky EGR valve.

Obviously a vacuum leak is going send the duty cycle out of whack as the system tries to richen to compensate for the additional air, so before you check and adjust the duty cycle, ensure that there are no vacuum leaks.

You should be in good shape for the future as you now KNOW how to pass the test. You did a good job reading and understand all the referenced information on how to "tune for emissions", and this should be an example for all.

It shows how a little judicious "tuning" can turn a failure into a pass with lots of margin, notwithstanding the fact that you probably had a leaky EGR valve.

Duke

Well, both. And the fact that I had to readjust duty cycle after the EGR valve replacement indicates there may indeed have been a vacuum leak. Also, I measured vacuum at the intake manifold after EGR valve replacement. It was 15 mmHg at idle and 20 mmHg at 2000 RPM. This would be in agreement with figures posted elsewhere on the forum (I believe by you, Duke).
Thanks again, Bruno

It's inches Hg not mm, but IIRC 15-16" at idle is about what my car shows.

Duke