92 gxe with 114000 miles just failed the emissions test in WI. HC .0498 grams/ mile limit .80 , passed
CO .0360 grams / mile limit 15.00 passed
NOX 4.5616 grams/ mile limit 2.000 FAILED
This is the first time ever that the car failed. The car has been running fine since I replaced one fuel injector about a month ago.
Any suggestions, I don't have a lot of extra money to put in this car.

 

well Im thinkin its a sensor or actuator that is present to control NOX, but is malfunctioning. The one thing that I definitely remember is the EGR valve. Its there to reduce NOX. Unfortunately I have a massive brain fart and cant think of the others that control it. But I would start there if I were you. Good Luck

 

High Speed Low Speed
Standard Current Reading Standard Current Reading
HC 120 193 124 446
CO .67 1.69 .69 1.58
Co2 13.9 13.9


Readings from my failed inspection. I replaced the spark plug wires distributor and ignition rotor and that solved it also got an intake cleaning. So it looks like you don't have to do those things since we didnt fail the same things.

 

NOx forms when temps in the cylinder reaches above 2500 degrees. Some causes are malfunctioning EGR system.

Ill post some more info tomorrow.

 

My VE failed NOx. It is definitely a component of the EGR system, I bought a new cat after thinking the EGR was good, turns out I had misdiagnosed it. The EGR opens and closes using vacuum, and there is a solenoid that controls the vacuum feed to the valve itself. Make sure the valve itself isn't sticking or clogged, then check to see that the solenoid is working, and that the ECU is sending a signal to the solenoid. Finally, make sure the vacuum source going to the solenoid and/or valve is good. That was my problem. I used the vacuum coming from my V/I valve (I have a VE engine) and the EGR valve started working again! Good luck. I HIGHLY suggest you invest in a Mity-Vac, they are $20 at Autozone and help immensely with troubleshooting vacuum issues.

Mike

 

The NOX seems high at low and high speeds if I am reading the chart they gave me right.

 

Where is the EGR and what does it look like?
Is this something I can test with little experience?

 

Define "little experience". Read my thread about my experience, it has lots of good info.

http://forums.maxima.org/showthread....&highlight=NOX

 

If its EGR dirt, its DIY job. Just check the vac hoses for cracking. Also check EGRC temp sensor readings. clic: http://www.cardomain.com/memberpage/748507/3

 

if he's failing for NOx it's not because the EGR is open, it's because it's closed.
the EGR when open adds exhaust to the intake mixture to help cool down the combustion chamber temp IIRC

 

EGR is bolted to the upper intake manifold. i would say it's under the IACV area. there's a metal tube that connects to it from the front exhaust manifold. the top is a round and there's a diapham under it that moves the valve up and down.

start the car...get out and carefully place your finger under the diapham and rev the motor. it should move...if it's dead then figure out what you need to fix it.

 

...and looking at the diagram: spring closes the EGR valve, if no vacuum. Hose leak?

 

Vacuum will only be supplied to the EGR valve when the EGRC is commanded by the PCM. There may be a vacuum leak between the EGR and the intake, the EGRC could be malfunctioning, or the EGR valve itself could be bad. A previous post recommended using a Mityvac to test the EGR and that's a good idea. If not available suck on a hose attached to the EGR and see if it opens. There may be carbon in the seat are of the EGR causing problems.

If all else fails try the ole tune up in a can trick. They have the emission pass crap they sell in parts houses that do work sometimes. I had a friend in Houston pass recently using that "snakeoil". Don't ask me how it works as I'm no chemist.

 

I just failed as well.

Original reading(w/fuel injector cleaner in gas)
NOX 2.441 grams/mile. Limit: 2.000 Result: FAILED

I hoped that maybe(juuuust maybe) the fuel injector cleaner being out of the system, would tip the scale in my favor......After a few more tank fulls of 93octane...

NOX 2.211 grams/mile. Limit: 2.000 Result: FAILED

Oh well !!

I can hear a vacuum leak of sorts mainly upon acceleration, so I will be looking at the EGR myself. Probably between 45-60 days from date of failure

-Jim

 

There is one small hose that was off on the left side of the unit. Could this cause the high NOX?

 

yes, see if you can plug it back in.

 

Any of the EGRV hoses leak causes EGR valve to close:

 

I barely passed the Cal emission test due to high HC. What causing high HC, anyone?

 

Running too rich........could be bad O2, leaky injector, timing, etc........there are many possibilities.

 

So we cleaned the EGR and lines to and from it, checked to make sure it was working , replaced a hose to it, and it still failed.
Is there a way to check the cat coverter by yourself or do I need to pay someone to do it?
Any other suggestions?

 

You are sure it opens and STAYS OPEN when you move the throttle? Is the EGR exhaust tube blocked? I really doubt it is the cat. At what vacuum reading does it start to open? What vacuum is it receiving?

 

Maybe u already mentioned, but: The trivials - wires, plug, cap??

Then the connectors, groundings etc oxidations causing erroneous input, voltage loss etc.

See for 80k garageKing max, alt gnd white cake, rust:
clic http://www.cardomain.com/memberpage/748507/10

 

1. do you have an infrared thermometer?
2. your cat affects your HC and your CO levels, not you NOx level

 

Well we finely got around to changing the o2 sensor today. Took it for a drive and went in for the test. PASSED
Thanks to all of you for your help.

 

Speaking of O2 sensors - any place that has them new for dirt cheap?

 

Sstein: Insert something under the EGR valve membrane. That way you will force it to stay open and hopefully pass the emissions. You can deal with the valve later at your leisure.

 

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