FAIL!! 800 out of 575 NOx

C

CanukRunner

New member
SO I did my etest and I got me a big FAIL!!

(98 3.4 V6)

My CO was 26 which from my understanding is hydro carbons and is fine so no blown engine.

But my NOx started as high as 1200 then got down to 800 but the pass was 575. My understanding of this is that my cylinder temp is high from running lean , not enough fuel to the cylinder.

I do have a one year old crappy generic cat, possible obd1 not 2.

I have just replace the rear o2 but not the front.

They suggested EGR valve (which im not sure i even have) or a vacuum leak.

Anyone know how to diagnose vacuum leaks??
 
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well i dont know why you replaced the rear o2, it does nothing to affect how the motor runs, all the rear o2 does is tell you if your cat is working or not. the front o2 sensor is the one that will affect how the motor runs ie rich or lean ect. so id start of will a new front o2, then try like new plugs and wires. maybe clean the TB, and MAFS, and possibly put in a new air filter... change the oil, take if for a good drive to make sure the cat gets nice and hot(up to normal operating temp for like 20min should be sufficient and then retry the emissions test.
 
t4r4life said:
hi nox means the actual filter is bad so you might need a new cat
Click to expand...

or he didnt get it hot enough to burn off all the "excess". what brand o2 sensor did you get. and you should still replace the front one.

it does not matter how good of a cat you have, if the motor is running TOO rich or TOO lean the cat can not make up for this... the front o2 will help bring the "variances" back in to "check" and with in the cats parameters to do its job. also if you have a cheep or bad rear o2 sensor it will not tell you accurately if the cat is doing its job or not. also cheep cats are just that, cheep cats, they will "get you by" but they are not going to last.
 
I bought the Denso from Rock auto, I got a code saying the sensor was bad. I also watched it on my torque app for android and it didnt do the up and down sign wave thing so i replaced it and now it seems to be acting properly.

I should replace the front 02, its also the original from 1998. It seems to be working on the torque app ......but to change it I need to cut out the piece of pipe and weld new in..so i may just try to find a good cat cheap...er as the replacement of the 02 would be 120 anyway.

I still wouldnt mind making sure i have no vacuum leaks so im gonna try a few ways of finding those first.
 
You seem to have some strigent emmissions, here in CT if the car turns on and doesnt have a check engine light, you are in the clear, everything on the sheet i got back was N/A, when i first got it sniffed in 09 they put the tailpipe sniff thing in, and my tailpipe was not even connected to the rest of the exhaust.

I would do as everyone said with the tune up, then i would just drive it hard, so that the CAT burns off all the crap that builds up in it, and bring the truck to get sniffed while its still warm.
 
I would also recommend a bottle of injector cleaner. (I've had good luck with the redline brand). Your o2 sensors are reading multiple cylinders, so if one injector is leaking a bit and causing a single cylinder to become rich, the sensor will lean out everything trying to compensate. You should be able to see that in your fuel trims as well if your scan tool shows them.
 
I don't have emission testing in my great state of Louisiana, so I may just be making an ass out of myself.

But, doesn't premium fuel usually help people squeeze by on emissions test to?

Going over my highschool chemistry in my head I would think that would have more to do with Hydrocarbons then NO, but I'm unsure.

Anyone know if some premium fuel would help him out?
 
I suspect it is the cat or non-OEM O2 sensor.

I have been running a K&N CAI and flowmaster for like 7+ years. I have never had any smog issues.
 
smog w/high nox

Been there done that.
Had a problem with NOX, everything else was fine, granted my t4r has a lot of mods. Replaced plugs, wires, pcv, fuel filter, oil & filter, air cleaner, ran injector cleaner through it, cleaned TB and MAF. No change, replaced the cat and made sure it was good/hot and it passed. There are several aftermarket CARB approved cats for less than $200 here in cali so my guess is you should be able to find something cheap in your area if you go that route.
hope that helps:driving:
 
bikerjosh said:
There are several aftermarket CARB approved cats for less than $200 here in cali so my guess is you should be able to find something cheap in your area if you go that route.
hope that helps:driving:
Click to expand...

Not to pull away from the original posters thread, but any idea how those cats relate to the later model CA emissions trucks? particularly my 2000 dual cat PITA.
 
Stick Figure said:
Not to pull away from the original posters thread, but any idea how those cats relate to the later model CA emissions trucks? particularly my 2000 dual cat PITA.
Click to expand...

Not sure, my t4r was originally sold in AZ, so I think those only came with 1 cat. My guess is you might be able to get two cheap ones? My aftermarket one is a Wagner if that helps.
 
I too would be interested in finding an obd2 cat... Apparently my 130 dollar one is a higher flow obd1.. at least that's what the guy at zorro said...

I bought this 02 for me rear ... It looks shiny enough to be stock..lol

http://www.rockauto.com/catalog/moreinfo.php?pk=991722

Also what is this fuel trim thing you speak of? that sounds like it makes sence.. i have the torque app for android....

What should the fuel trims be and how do i read the numbers?

Thanks!!
 
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