another emission test failure...high NOx...help

Just had my emission test done today on my 92 (automatic, 302 000km, Toronto, Canada) and it failed quite badly. (went to the Drive Clean facility on Warden, south of 401, in Scarb.)

On the dyno: On idle:
HC ppm: Limit=66, reading=28 Limit=200, reading=141
CO%: Limit=0.37, reading=0 Limit=1.0, reading=0.8
NOx ppm: Limit 505, reading=1395

Technician mentioned replacing EGR valve, checking cooling system, retarding timing, excessive deposits on exhaust valves.

I’ve noticed that the car has been “burning/using up” coolant lately. The overflow bottle is near the MIN mark and after filling back up to the MAX mark twice, the level seems to drop. There are no coolant spills on the ground under the car, no smells after a long drive. I did notice corrosion at the end of the upper coolant hose at the head, looking like battery terminal corrosion.

I don’t think its the catalytic converter judging by the other two measuremnts other then NOx reading.

I plan on 1) changing the EGR valve, 2) flushing all coolant, 3) replacing spark plugs with OEM ones, 4) putting the old intake back on (I have a K&N cone filter with pipe).

Any suggestions/feedback as to what other things I can do??

Much thanks.

A lower temp range thermostat may help a little. IIRC, NOx emissions exist primarily because of the high temperatures experienced during the combustion process. If you can lower the operating temp of your engine a few degrees, it may make a difference.

Also check your oil and make sure it looks normal. If your headgasket is starting to go and you’re getting antifreeze into your oil, obviously that’s going to affect your emissions.

Just so you know, with regard to the intake, I doubt it will make any difference. I just had my Integra emissions-tested last month and it’s got an AEM SRI, 160,000mi, and I passed with flying colors.

I would do as RioGS suggested; lower your operating temp, and make sure to run a can of Seafoam cleanser through the car before testing… this will help to clean away some of the deposits on the valves etc. which may help as well.

Good luck!