92 SENTRA HIGH NOx Emissions HELP!

[sock_s]

I have a 92 Nissan Sentra 1.6L with 185,000 miles. For the last four years, I have had trouble passing state emission standards. Every time, my NOx emmissions are to high. I have done the following with no avail: changed spark plugs, used super unleaded fuel, cleaned out EGR valve, replaced all cracked hoses to the EGR system, cleaned throttle body, cleaned MASS airflow sensor, replaced air filter. The catalytic converter was changed 5 years ago. O2 Sensor changed four years ago. Any help in getting my car to pass would be greatly appreciated. I have run out of ideas.

[SR20B12]

what are the tree huggers trying to tell you . and where do you live?

try a compression check . it can't hurt. loss of compression will add to this . with 180,000+ it would be a cheap what if.

[nhladky]

To be honest, cleaning out the EGR valve generally may help, but if emissions persist, then replacement is highly recommended. Another common reason for failure is poor oil/oil filter condition. The best thing you can do for this is of course replace it. Recommend Mobil1 Synthetic 5W30 which has done well by me, along with restoring ~3hp at the wheels. Another item I would seriously inspect is the Cat. You stated that you had it done 5 years ago, but what may make a huge difference is who's Cat you put in it. There are "knock offs" as it were, that will do the trick for a few years then be completely uneffective. I would strongly suggest looking into this as well and perhaps researching or reporting the make/model of Cat used. Someone will know if that's a good part or not. There are 3 more things you can look into as well. 1- Check your timing, make sure it is set to mfg specs +-1 degree should get most emissions under control. 2- Don't just clean the MASS airflow sensor, replace it. 3- Make sure your engine is running at true operating temps before taking it in for emission testing. Your engine is most efficient when it can burn raw fuel rather than burning reusable emissions. Oh, I guess there is a 4, replace the O2 sensor. Keep in mind that the oil on your skin is enough to knock that sensor out of wack enough to fail emissions, so make sure no part of the sensor below the tightening bolt is touched or bumped by hands or grease.

Hope that info helps! If all else fails, you can always change your injectors and have your fuel mixtures adjusted- I'd recommend if you havn't done this before on any import vehicle, that you take it to the dealership or a trusted mechanic (if you can find one) to get this work done.

Happy wrenching!

[yogi_123rd]

Suggest you replace the EGR valve instead of clean it. Went thru the same pain of those demanding state inspections (5 times). After replacing the EGR, the high NOx dropped by 80%. Replacing the ignition components (plugs, wires, etc) just seemed to drop the hydro-carbon values by a small percent.