bored smog tech here

[blackrms13]

I know this is a old thread but I just failed my smog

91 S13(about 115k) with a stock 95 OBD-I KA(68k), I believe it is a non-cali engine

New Plugs/Wires (about year ago)
New O2 Sensor (2-3 weeks ago, but the tech said "something is wrong with it b/c its running very rich)
2.5inch catback

NO reading is like 7xx max right?
I got like 3000+ reading...

i warmed up my car pretty well before doing the smog(drove from riverside to LA, about 1 hour)

I know the timing is off for sure(well after the test....) need to find a timing light first
gas cap failed(bought a new one right afterwards)

from reading this thread, i assume its time for a new cat?

thanks to whoever can help

[SoguRacing]

Originally Posted by blackrms13

I know this is a old thread but I just failed my smog

91 S13(about 115k) with a stock 95 OBD-I KA(68k), I believe it is a non-cali engine

New Plugs/Wires (about year ago)
New O2 Sensor (2-3 weeks ago, but the tech said "something is wrong with it b/c its running very rich)
2.5inch catback

NO reading is like 7xx max right?
I got like 3000+ reading...

i warmed up my car pretty well before doing the smog(drove from riverside to LA, about 1 hour)

I know the timing is off for sure(well after the test....) need to find a timing light first
gas cap failed(bought a new one right afterwards)

from reading this thread, i assume its time for a new cat?

thanks to whoever can help

if your NOX reading is high then you're running lean not rich. NOX is the production of excess heat in the combustion chamber. a lean condition will cause the NOX number to be excessively high. If all your other numbers were fine, it's not the cat. Try retarding your timing a bit or getting a step colder plugs. this may help.

[touge monster]

Originally Posted by SoguRacing

if your NOX reading is high then you're running lean not rich. NOX is the production of excess heat in the combustion chamber. a lean condition will cause the NOX number to be excessively high. If all your other numbers were fine, it's not the cat. Try retarding your timing a bit or getting a step colder plugs. this may help.

Had the same problem.

new plugs and re-adjusting your timing should make it pass.

[blackrms13]

Originally Posted by SoguRacing

if your NOX reading is high then you're running lean not rich. NOX is the production of excess heat in the combustion chamber. a lean condition will cause the NOX number to be excessively high. If all your other numbers were fine, it's not the cat. Try retarding your timing a bit or getting a step colder plugs. this may help.

the guy who previously had my engine said he put in some new Iridium(sp?) plugs a few months ago

should i switch back to the normal Copper ones?

thanks


heres more info regarding my problem
http://zilvia.net/f/tech-talk/223732-smog-problems.html

[idlafie]

Originally Posted by SoguRacing

if your NOX reading is high then you're running lean not rich. NOX is the production of excess heat in the combustion chamber. a lean condition will cause the NOX number to be excessively high. If all your other numbers were fine, it's not the cat. Try retarding your timing a bit or getting a step colder plugs. this may help.

High NOX readings is the result of your Exhaust Gas Recirculation, (EGR) system not working. You could have a cut, melted or split vacuum line or bad soleniod somewhere in the EGR system...You'll need a Factory Service Manual to trace the lines & fix the problem.

The purpose of EGR (Exhaust Gas Recirculation) is to reduce the NOx emissions by putting a portion of the vehicle's exhaust gas back into the intake manifold so it mixes with the fuel and air in the combustion chamber. Air is mainly made of oxygen and nitrogen (O2 and N2). At temperatures above 1300°C (2372°F), these molecules split apart and rejoin with each other to make nitrogen oxides (like NO, NO2, etc...).

By adding hot exhaust gases into the combustion chamber, you are lowering peak combustion temperatures. The lower temperatures prevent the O2 and N2 from splitting and combining. Even though the exhaust is hot, about 600°C (or 1112°F), it's much cooler than the 1300°C required to make NOx.

In summary, the exhaust adds mass, increasing the heat capacitance of the mixture (i.e. making it harder to heat up the mixture in the cylinder). Peak temperatures are lower, reducing NOx formation, which ultimately reduces smog in the environment.

[lflkajfj12123]

Originally Posted by idlafie

High NOX readings is the result of your Exhaust Gas Recirculation, (EGR) system not working. You could have a cut, melted or split vacuum line or bad soleniod somewhere in the EGR system...You'll need a Factory Service Manual to trace the lines & fix the problem.

The purpose of EGR (Exhaust Gas Recirculation) is to reduce the NOx emissions by putting a portion of the vehicle's exhaust gas back into the intake manifold so it mixes with the fuel and air in the combustion chamber. Air is mainly made of oxygen and nitrogen (O2 and N2). At temperatures above 1300°C (2372°F), these molecules split apart and rejoin with each other to make nitrogen oxides (like NO, NO2, etc...).

By adding hot exhaust gases into the combustion chamber, you are lowering peak combustion temperatures. The lower temperatures prevent the O2 and N2 from splitting and combining. Even though the exhaust is hot, about 600°C (or 1112°F), it's much cooler than the 1300°C required to make NOx.

In summary, the exhaust adds mass, increasing the heat capacitance of the mixture (i.e. making it harder to heat up the mixture in the cylinder). Peak temperatures are lower, reducing NOx formation, which ultimately reduces smog in the environment.

thank you for explaining the point of the EGR system to me

never knew that