Alright so the HC and CO passed with flying colors but my NO(PPM) was really high. At 15mph my NOx measured 863 with a Max of 689 and at 25 mph it measured 1236 with a Max of 706. What causes a high NO reading? Any help would be great

 

Could be from carbon build-up on the valves.

 

The egr system is supposed to reduce nox. Try checking that out make sure nothings clogged or dirty and its operating properly.

 

So i took of the EGR and noticed that there was some carbon buildup blocking the passage on the intake manifold side. I hope that was the problem, is there anyway of testing the EGR to make sure its functioning properly?

 

There are a couple of ways. One is to reach back to the valve with the engine running and press the diaphram (sp?) on the valve and see if it changes the idle. The other is to use a small hand held vacum pump and attach to the vacum line going to the EGR vavle. Apply vacum and see if the idle changes. Most likely, if the valve is functioning, the engine will die when you activate the valve (or at the very least will really go down in RPM).
One more sugguestion would be to replace the EGR valve. As old as these cars are at this point, it is just a good idea. (However, that is just my 2 cents)

 

Is that a "typo"? Did you really mean NOx measured 863......

Could be running on the lean side, or on the hot side. Both will increase NOx production.

 

egr test, get a hand op vacuum pump about 30 bucks at kragen connect it to the EGR hose when you apply vacuum the valve will open and let a lot of exaust gases into the intake manifold the engine should balk and maybe stall if not remove the EGR and clean it it may be sticking. you may also have a bad catalyst talk to a smog guy.

 

Yea that was a typo haha sorry, It was my NOx that measured 863

Later on today I will try the EGR test and see if its bad or not. The cat is only a week old so I know that couldnt be the problem. I have also heard that running lean could cause high NOx readings, is that true as well?

 

 

Maybe check your catalytic converter(s) too. Could be lots of things. High combustion temperatures cause high NOx numbers also. Maybe youre running too rich.

 

Running rich will increase HC and CO, while reducing NOx.

 

You really have to read the results and narrow it down from there, most the guys at the smog places don't know any thing. I would look at what Injuneer is saying and search this board, thats what I did and was able to get my car sorted out.