My 1987 Vanagon failed its Arizona emission test this morning. Results were Hydrocarbons (HO) grams/mile .75 limit 1.60 (passed), CO grams/mile 25.73 limit 15 (failed), NOX grams/mile 2.91 limit 2.5 (failed).
I have the standard printed list of what might cause these results. The last time it failed 2 years ago, it failed only the NOX reading and I had to get a new catalytic converter that cost over $500
I've noticed the low-speed engine fan comes on a lot more than it used to and sometimes it even goes to high-speed which is a scary thing because it makes the entire vehicle vibrate and I can feel it through the gas pedal.
According to the testing station you can request a second-by-second graph of the emissions test but they will only fax it to a repair shop.