Failed smog Any suggestions on what i could check or what the problem may be if my 92 protege failed smog by having hc's and nox to high. my hc was 190 with 127 max and my nox was 2021 with 825 max.

did you start with a basic tune up ? plugs, air cleaner ?coil ? on what ?is your catilatic convertor good ?

Other than testing the EGR valve, not many options. You really need a 4 gas analyzer to know what is coming out of the tailpipe. Otherwise you won't know if repairs have helped the problem.
When you say EGR numbers I'm not sure what you mean. Most of the time the test is for CO and HC gases, along with oxygen and Nox also in some areas. The EGR valve allows some exhaust gas to be recycled thru the engine and reburned. CO or HC could be high if the EGR system is not working.

wow, no context but i can read your mind?
ok SMOG failed. right?
what speed, there are 2 in uSA, 15 and 25.mph.
so there are 3 tests, which one. all are PPM in usa.
parts per million.
but is that HC , CO, or NOX? or ?

based on your numbers is HC
hydrocarbons or in barstool, its raw gasoline leaving rear of car.
unburned fuel..

572 ppm is way too high 12-19 is normal
id say the CAT is bad.
but can be , engine is bad, and burned out the cat.
that is why all savvy mechanics, check the that the engines
holds closed loop status, (EFI closed loop) at the speed yours failed.
if not in closed loop the cat will burn up (rich)
that is first.
Once that is cured. you check HC again. if out of spec
you did burn up the can , new cat time.

that is the correct way.

If the plug wires are original replace them with a quality set and also do the plugs. If the car still fials you will need to replace the catalyst.

fist i would like you to post the year make and model of the truck along with the HC ppms and NOX ppm it would be very helpful but high hc and nox can be attributed to a faulty EGR system nox is produced when the combustion chamber temperature gets too high so a small amount of exhaust is cycled back into the air stream to help cool them there are other causes but without looking at the levels its much harder to say

Check your oxygen sensor, idle speed sensor & the idle air sensor your sensors wil effect. the emmision test.

means that the hc,co2,nox, emissions are too high, you will need the numbers in ppm on the read out to begin diagnossis

Question

PPM of Nox or Co or HC?????


The base of the EGR and the EGR air passage tube will collect carbon over the years.

Most car over 65,000 will fail Nox and has high CO because of the partly block passage.

The only way to clean to the air passage tube is with a lot of WD-40 or similar cleaner.

The EGR valve can be clean or replace under $68 ////gasket for around $3.

Make sure there is NO LEAK when you put the EGR valve back in place.


Please post what PPM is failing on reply.

have your EGR system checked . sounds to me like its not working or clogged

nox is from running lean..... its realy high temps that cause this.......... replace the o2 sensors this should cure that any more help let me know