so i have searched the forum for any problems with nox readings and was looking to get some help with my emission test. From what i have read everyone who has failed nox portion has failed by almost triple the amount. i figured it could be my o2 sensor but i always thought that any problem with an o2 sensor would result in a check engine light? i was thinking to rule out the cat because everything else passed but i may be wrong with this assumption.The cat might also been cold. i had taken it to the shop and then brought it to get e tested so i only drove it for 10 minutes so could that cause such a great difference in my Nox reading? if anyone could help and give me tips to pass the test that would be great. I need to get this car on the road for work so any help would be greatly appreciated. by the way here are my results
40 km/h curb idle
limit reading limit reading
HC ppm 68 33 200 35
CO% 0.38 0.35 1 0.03
NO ppm 0526 807

RPM 2070 750
dilution 14.43 13.93

 

run colder plugs.
check you're timing, it might be a bit lean.

 

tbh if you dont wanna deal with it there are places you can get it "passed" for an extra few bucks I have done it on previous cars. but as for the problem i dont know what it could be.

 

+1

High Nox would be from running a bit too lean

 

nox means the combustion temps are too high which is caused by running lean or too hot of a plug

 

now would running that lean cause the nox reading to be 300 over the limit or could there be other contributing factors?

 

yes and yes

 

ok sounds good. ill check the timing and get some plugs. Any suggestions on what plugs to get. Is the stock timing 16? Thanks again for all the info everyone hopefully this passes

 

here's the part number for the plugs you should get. these are 1 heat range cooler than what it calls for.

NGK V-Power
ZFR6F11

or

NGK G-Power
ZFR6FGP

 

Nox is normally your cat. I fix car's that have failed the e-test at my shop. And 95% of the time it's going to be your cat.

 

thanks for the input really appreciate it. Is there any way to check if it is the cat? i havent heard any rattling in my exhaust but i cant rule out the cat is still good. are there any brands you would suggest for a cat or should i just go oem?

 

to test your cat get your car at temp the hold rpm at 2000rpm and mesurse tep at front and rear of cat it needs to be at least 100 degress f hotter on the out if not cats no good. youll need a inforred or leaser thermomitor for the test and someone to hold the rpm

 

You need to have a sniffer machine like the places have. My work has a 5 gas analyzer that we uses to see what the numbers are. The cat will not make noise always. It breaks down on the inside, and it also get clogged with build up over the years from all the air and fuel that goes through it.

That works aswell, but it's some times still passes the test, so it's not a 100% for sure test.

 

hey guys thanks for all the help. passed the test today. it seems that the place that did mine the first time kept passing the rpm limit which in turn screwed up the nox reading. So i ended up taking it to another place, made sure the cat was hot (drove it to guelph and back from cambridge) and passed with flying colours.

 

thats great news glad you passed it.