My Ex failed emissions test. Can someone tell me what these numbers mean?

[old mechanic]

And possible fix needed for what my Ex failed.

reading limit pass-fail
HC- Grams per mile- 00.59 02.40 pass
CO- '' " " 009.66 060.00 pass
NOx-" " " 04.17 03.00 FAIL
CO2 " " " 336.84 N/A N/A

As you can see the NOx failed. I don't know whats up with the CO2 reading also.
I would like to narrow it down as close as possible if possible.
I changed the oil and filter two weeks before the test and put some complete fuel system cleaner in at the same time. I put new Motorcraft platinum plugs in about 5 days before test removing battery cable while doing work. Plugs gaped at .0054 Seems to be running pretty good except for a very very little rough idle.
I was going to replace the o2 sensor and clean the MAF but I didn't because I thought it was running good enough to pass.
Thanks, old mechanic.

 

[spindlecone]

Your Cat is most likly defunct

 

[Maniak]

As I understand it.. high NOX means high combustion temp..

The EGR is what is supposed to cool it down.. It is possible the EGR isn't working or the EGR tube is blocked...

Also, if the O2 sensor is off (e.g. not giving the correct values) you can get a high temp reading as the mixture will be off.

Timing can also increase temp, but I doubt that is off on a computer controlled vehicle..

Thats all the input I think I have.. I'm sure you will get more/better info from others..

~Mark

 

[spindlecone]

would still think the catalytic convertor, yours if orig is 14 yrs old, it's main job is to lessen NO2 emissions.
also as the above said, Hi combustion temps, perhaps caused by a restricted cat

 

[Glacier991]

High NOx readings occur when events combine to allow atmospheric nitrogen to combine with the burned gases in the combustion chamber. Generally that means higher than normal temperatures. Circumstances that can lead to abnormally high NOx emissions include:

* Malfunctioning EGR valve

* Lean fuel mixture (AFR above 14.7, Lambda above 1.0) This should be rare on modern computer controlled vehciles with 02 sensors..... but not impossible if a sensor is bad....

* Improper spark advance ( I had a Honda once that failed because of an oil soaked connector at the distributor causing this issue)

* Thermostatic air heater stuck in the heated air position (pretty rare but possible)

* Missing or damaged cold air duct (it's all about heat, see?)

* Combustion chamber deposits... more common in older engines....

* Malfunctioning catalytic converter... also more common in older engines.

That is the laundry list.... the spark advance is not adjustable, but you can pull the knock bar ( that is not the name I am looking for ...but it is a little connector that, when removed, reduces the spark advance) and reduce the advance which can help....

The advance per se, on computer controlled engines is not adjustable.

Hope this helps.

 

[old mechanic]

Thanks guys.
According to my manual and a old thread I found here where Robb and 410Fortune said that a 1992 EX does not have a EGR valve. So now I guess i'm looking at replacing the o2 sensor, the cat or both. I'm going to clean the MAF anyway. My EX has 100,000 miles on it anyway so I guess maybe I should just replace both??? I just am afraid that if I replace the cat I will end up replacing other exaust parts I may screw up taking the cat off.
Also will a universal cat be ok for my EX as they seem much cheaper?
Thanks again old mechanic.

 

[savagefan]

Before you change the cat, try a carbon cleaner like sea foam, nothing to lose and if it doesn't help why pump gunk into a new cat, good luck.

 

[Glacier991]

100,000 miles is an early cat failure. I am doubting the cat, but heck, in these situations one can often never tell. But I'd do the CAT LAST!

 

[1IronMike]

Make sure the air intake system is all tight. My wife took her car to a shop for a tune up when I was out of town and they left the rubber duct between the MAF and plentum loose on one end. Car ran like crap with increased RPM's and rough idle. Tighened it up, calmed it right down. Granted it was not due for SMOG yet but it sure would have caused a problem.

 

[old mechanic]

100,000 miles is an early cat failure. I am doubting the cat, but heck, in these situations one can often never tell. But I'd do the CAT LAST!

-------------------------------------------------------------
Same thing I thought for my EX but I only have one free re-test then I have to pay full inspection price again. Since I don't have a EGR valve and it runs so good I am going to replace the O2 sensor and cat which are the two parts you guys are recommending to replace and go for the re-test.
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I read that the cat is to reduce three things:
1- CO
2- VOCs
3- NO & NO2=NOx Which is what my EX failed.
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I read this about the O2 sensor:
When the oxygen sensor fails the computer can no longer sense the air/fuel ratio, so it ends up guessing. Your car performs poorly and uses more fuel then it needs to.
Also says that if there is a lean mixture from a faulty O2 sensor that will cause higher NOx pollutants which is what I failed.
Although my EX does not perform poorly it does seem to use more fuel than some others I know of.
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My thanks to everyone and i'll let you know what I did and if it passes.
Old Mechanic.

 

[Grey Owl]

Not sure if you have one on the 92, but my 94 has a "Delta Pressure Feedback EGR" system (california emission equipped). The sensor is the module on the left side of intake, near the TPS switch. Has a 3 wire plug and 2 vacuum hoses going to it. This item is a common problem - in fact, Ford has had several "upgrade" replacements for this sensor. Ford recently came out with a NEW version - this new one requires a replacement of the wiring connector (included) - and you have to be very careful to follow wiring diagram EXACTLY. Otherwise it bolts in and connects as the old one. The new part number is 4W1Z-9J460-AA. Don't let dealer sell you older version. I replaced this sensor (again) with this newer one - reset the PCM - and no more problems.

 

[IAmTodd]

DPFE is only on vehicles equipped with an EGR valve(hence why E stands for EGR). I'd run a can of sea foam through it and see what happens.