reno928s

Two years ago I passed without failing. This week I went for inspection and failed for NOx. The only change I made was the radiator to a griffin. I'am wondering if the car runs cooler would it affect that part of the emission? And if so How can I correct the problem? TIA, Reno

wi54545

Check your vac lines. I think a high NOx is a lean condition.

Ballistic-Chapman

I found these thread useful:
https://rennlist.com/forums/showthre...&highlight=egr

https://rennlist.com/forums/showthre...&highlight=egr

lejams

NOX is a rich condition. I have leaned mine out with a AFR and passed.

Ski

yep, lean it out and turn on the A/C.

jns

Also, just changing the oil and adding some fuel treatments such as "emissions test passer" or the fuel additive in the little pink bottle (forget the name) along with getting the exhaust system heated up good after a hard drive before testing can help. Good luck!

reno928s

just to give you an idea here are the numbers HC- Standard 173 my reading 136 pass / NOx-Standard 1323 My reading 2342 Fail. i would like to correct the problem if possible. Will I need to bring it to a mechanic so he can adjust the air fuel ratio? And from reading the above board it seems that I am running very rich. I missed it by a mile. Reno

Waterguy

Reno, if you are getting high hydrocarbons and high NOx together, it usually means something is worn out or failing. Assuming that your car is in good shape, in tune, etc., the usual culprits for causing this are the oxygen sensor and the catalytic converter. You might think about a tune-up if its been more than 12k miles, replace the O2 sensor and have your mechanic set the idle CO. After that, if it still fails it is probably the cat.

Trucho-951

Normally a rich condition will keep the combustion chamber temperature rather "cool" and keep NOx levels down. However, if the car has been running rich for quite some time, then the opposite will occur because excessive carbon build-up inside the camber could be glowing red hot and causing hot spots that will create high levels of NOx.

A new catalytic converter will keep NOx levels low, but, before forking out the dough for a new catalytic converter, I would suggest using a fuel additive that will clean out the carbon deposits from your valves and combustion chamber, for example, the "Emissions Test Passing for Dummies" by Gold Eagle. You can buy this at any Kragens parts store. Pour it in your tank, fill'er up, and drive around for a few days to a week prior to your smog test. Also, remember that the oil can absorb high ammounts of hydrocarbons, so it's always a good idea to get a fresh oil change prior to a smog test to help keep the HC's and CO's as low as possible.

reno928s

One last question, is it possible that the new Griffin radiator cools the motor to well that it does not get to the proper operating temperature, therefore creating higher NOx? As long as it's correctable, I will bring it to my mechanic to have the co level fixed and have the oil changed as well. Thanks in advance for everybodys help, Reno

reno928s

Any input on my last question?

EdC

I would think that your thermostat would regulate coolant temp to the engine, even if the new radiator was better at cooling the coolant than the old one.

Kevin Baker

Reno, what were the RPM's on the test? How do they compare to the "standards" for testing. If the inspector was running the car near the lower end of the acceptable limits, they could try keeping the RPM's up and that would help. Also look at the O2, how do they compare to stoechemetric (sp?) 14.7 +/-?, and finally, when did the state last test the calibration of the test gasses? BTW I'm an inspector in Texas.

reno928s

I forgot to mention that I installed a cooler running thermostat in addition to the new radiator.

Trucho-951

Reno,
Since no one else is answering, here are my $0.02. I would bet that the high NOx leves have nothing to do with your larger radiator at all. In the past two years, probably your O2 sensor has gone out, an O2 sensor is only rated last 60k miles at best. With a bad O2 sensor, you have probably been running a little rich and hence probably have excessive carbon buildup in the combustion chambers and probably also inside the catalytic converter. Our cars are already known for emitting high levels of NOx. So our cars need a really good cat.

As I mentioned before, with excessive carbon buildup in the combustion chamber, there could be clumps of carbon that are glowing red hot (localized hot spots) and causing high NOx levels.

If it was my car, I would install a new O2 sensor, then add the fuel additive I mentioned above in post #9, fill up the tank of gas, and drive around for a week or as long as it takes to use up the entire tank of gas. This should clean out much of the carbon buildup.

Next, I would get new sparkplugs, and a fresh oil change. Take it down to the test station and ask for a "partial pre-test", I believe it's only like $20 to $25 for the partial. If it passes, then ask for the discount package to run the full test and get the certificate. Then go grab some beer and celebrate.

If it doesn't pass, well... then you might actually need a new catalytic conveter.