Failed MA Emissions for NOx

[masho95]

Well went to get a inpection sticker today, passed the saftey, but failed emissions. HC and CO passed with flying colors, but the NOx readings sunk the boat. Here's the graph of my emissions output.

And here's the Emissions Results:

Emission -------------------- Reading ---------- Limit
HC grams per mile ---------- 00.57 ---------- 01.20
CO grams per mile ---------- 003.85 ---------- 020.00
Nox grams per mile ---------- 04.49 ---------- 02.50
CO2 grams per mile ---------- 380.46 ---------- NA

Sorry for the large picture, but you can really see the detail in it.
Any ideas on why the NOx is so high??? I have noticed recently maybe for the last few months that right after starting the car there is a gas like smell. It goes away soon after though, but perhaps something is going on here...

 

[Emerald94]

SPOUT! Pull the jumper.

 

[Yamaha V6]

Cats / vacuum leak

Edit...
Didn't you have a suspected head gasket or intake issue at one point, due to a Nitrous backfire in the intake, etc.?

 

[masho95]

Cats / vacuum leak

Edit...
Didn't you have a suspected head gasket or intake issue at one point, due to a Nitrous backfire in the intake, etc.?

Yeah, intake leak. the crossover tube was pushed away from the intake from the backfire. Pushed it back on and tightened the clamps and seemed ok. Also the backfire bent the throttle body plate (HUGE intake leak ) I did notice the right side gasket on the intake where the front surge tank meets towards the throttle body is slightly out of shape. Wish I had had the money for the group by BlueByU had set up... Anyways.

I thought that I'd mention that the O2's are also original! With about 106K on them. I doubt it'd hurt to replace them. Any thoughts on that?

 

[92ShoOff]

Hey Erik, welcome to the club of failing emissions. I'm due back for the 3rd time on Sept 8th, so this is my last chance. I already replaced my O2 sensors and added the Pro-M MAF, so that's almost $300 right there in parts. All I need is $450 invested in trying to get it to pass and then I get something like a 2-year waiver. So that said, I just used that as an excuse to by Mike's new Y-pipe and I'll be way over the $450 mark.

But definitely change those O2 sensors. You can get thos nice Bosch ones at AutoZone for something like $30/each. I wouldn't go with any other brand other than Bosch or Motorcraft for those though. Who knows, you might see your MPG go up a little. And use some anti-seize when you put the new ones in... helps get them back off really nicely if you ever need to.

 

[Rob94]

I failed for Nox back in 2000. I changed the ECT sensor and the O2 sensors, and then passed with flying colors. Worth a shot.

 

[masho95]

I failed for Nox back in 2000. I changed the ECT sensor and the O2 sensors, and then passed with flying colors. Worth a shot.

Brand new ECT sensor in there, so I guess I'll swap out those O2's and see what happens.

 

[94mtx]

i have had the same issue in cali with my 49 state car. (no egr) cant remember my nox levels but they were way up there as well with everything else being normal. changed cats with no difference. i have my thoughts, just curious as to how hot your engine is running? i think i have a hot engine situation. when i get back home i will really flush my cooling system and see if that helps. that wont happen right away, im in the middle east (bahrain) at the moment. my research leads me to believe that high combustion temps cause high nox, a few ways to get there. lean condition(maybe bad o2 sensors) and i think the cooling system is a stretch but its worth a shot. well let us (me) know so i can help clean up the environment by driving more!!

jon

 

[shosleeper]

nox is created when combustion temps exceed 2500 deg. The hotter combustion is the more nox produced. Given your relatively low CO, I would belive you are running a lean mixture. Lean means hotter. O2 sensor very likely out of whack. It could also be an air leak as was stated, or some type of fuel restriction (ie low fuel pressure). A 190LPM fuel pump my fix or even just some fuel injector cleaner.

 

[drdave]

I just had the same problem with my 93 with 180K on it. Didn't throw any codes, but I replaced the original O2 sensors and she passed with flying colors. I also replaced the mufflers (rusted Flowmasters) and ran a tank full of 93 octain through it. My Nox was much worse than yours seems to be.

 

[masho95]

Replaced the O2's with new ones as the ones that came out were stock O2's with 107K miles on them. Seems to be running somewhat better and the gas mileage as of now is looking better. I'll have to finish running out the tank before I get a firm number on that. And it'll probably go back to the inspection station on Saturday.

 

[92ShoOff]

Boo ya!!!!!! Installed my new Mid West SHO Y-Pipe the other day, and also bought some fuel additive at AutoZone. The additive says it's guaranteed to get your car to pass emissions or double your money back. The stuff helped a LOT the second time that I went through emissions (though just shy of passing me through it), and I gave the stuff another shot this last time with the new cats and everything went great! The lady was in the middle of the test (which usually takes about 3 or 4 minutes) and the screen on the computer suddenly went blank about 2 minutes into the test. I figured, "oh sh*t...... my emissions are so bad now that I just got an immediate failure." Next thing you know, the screen loads with the text "Fast Pass" in big letters. Never had that happen to me before with all the cars I've owned! Check out those figures!

If you didn't already get your car through emissions (or if you did and failed again) DEFINITELY go to AutoZone and pick yourself up a container of this stuff. It's in the fuel additives section, and the bottle is in a small box that says something to the affect of "GUARANTEED TO PASS EMISSIONS" on it. let me know how everything turned out Erik!

 

[Ferendon]

Guaranteed to pass, cause it burns amazingly clean... It's probably just alcohol and some other chemicals, 2 bottle of dri-gas and a bottle of 90% rubbing alcohol will work wonders too, but at the expense of the cats... Fried the cat on my truck after putting that mixture into the tank to pass emissions. 2 days later, no power, and it was blowing white powder flecks...

 

[shojuan]

Boo ya!!!!!! Installed my new Mid West SHO Y-Pipe the other day, and also bought some fuel additive at AutoZone.

The new cats in the y-pipe probably did a lot more for the emmisions situation than the guaranteed to pass stuff in a bottle.

 

[masho95]

I still haven't brought the car back for the emissions test yet, but just judging by the MPG I'm getting now I'm sure it's running way better. I think I have about 260 miles on the tank of gas I have now with over 1/4 tank of gas left. I was getting about just over 300 miles per tank (or when I usually fill it up, because I don't like running it that low).