Well I just wanna bounce ideas around as to why.
Hydrocarbons .53 allowed .60
Co .02 allowed .20
NOx 1855 allowed 700

I just fixed the egr system and it is now fully functional. All emissions components are present and functioning. Motor has 30,000 on a rebuild. Car runs great and getting 22 mpg averaging 80 mph. All ignition parts up to par/ new. No skipping. Fuel pressure 41 psi with Bosch III injectors. Cats aren't original. Np10 conversion. Timing set at 6*. Compression 145-155 psi cranking. No smoke ever. I do have a 3.5 full intake set. Running an 89 Maf tpi.
I have to pass this go around so I can drop in my 355. Then I can iron out the last bugs til I'm exempt. I'm thinking the cats are smoked?

 

http://www.smogtips.com/failed-high-...rous-oxide.cfm

5 main reasons:

Lean Mixture (o2 sensors, vacuum leak)

Faulty EGR system

Faulty Cooling system

Faulty Cat converters (I doubt this is your issue since HCs & CO are passing but I guess this depends how long the EGR and other components were is dis-repair)

Carbon Deposits (hi-mileage engine)

Remember Nitrous Oxide or NO is created when an engine's combustion chamber temperature reaches over 2500 F.
a engine that runs too hot will create excessive NOx. If you have not checked/serviced the cooling system, I would start with that.

 

motor runs 185* average. i just changed the water pump/ thermostat and flushed system maybe 7500 miles ago. o2 sensor is maybe a yr old. i did notice that the int was 146. blm is 130 at idle. the egr solenoid stopped holding vacuum a yr ago and i thought i got it settled. i finally replaced the solenoid and replaced all the lines. i cleaned the plenum ports/ intake/ all the way to the heads. this was in anticipation of the damn test. the egr is fully functional. ive been hunting the reason for the lean mixture for 2 years since i changed injectors. motor was apart 30,000 ago for a re-ring/ re-bearing. i normally rip them apart every 50,000 and take my measurements. when the egr went faulty the evap solenoid wasn't holding back vapors either. that was also fixed. recently. tps is set to .60. idle is 650 in drive at idle.

i am a diesel mechanic and have my own snap on scan tool. modis. thats why i included the data i have at present.

 

Ignition timing? your total timing could be too advanced, which would raise combustion temps.
Try setting base timing to "0". (which should have been the factory setting, was on my stock '88 with the 305 TBI)

Otherwise I would guess your EGR system in not right, your heads have carbon build up, your 02 sensor is lazy or dirty/clogged injectors causing excessively lean condition. what are you using for fuel? have you cleaned the injectors / replace the fuel filter lately?

You changed injector's to flow more fuel, or are they "stock"?

What about the A.I.R. system, is the smog pump working? check valve, etc. etc.
I'd check that also.

Lastly I would check / suspect the cat, but again with the HCs & CO passing that does not explain why the NOx would be off the scale.

 

Air - working properly.
Injectors - stock 19lbers from south bay with afpr
Timing - 6* from the sticker on the donor car. I can try 0* tho
Fresh 2001 tank upgrade with new filter 5,000 miles ago
O2 did seem lazy. can it really cause it that bad?



Figuring I work with this stuff daily I am stumped.