I drive a 95 nissan 240sx. car is stock except a Blitz catback exhaust. Exhaust has some popping, which i don't think is helping. Before the test did some maintanence. failed emissions the other day, got some questions for you guys about my readings.
CO - just a lil over the limitHC - just a lil over the limitNOx - DOUBLE the limit
Other than checking to see if my EGR system is working what else could it be that is cause this?Also how do you check to see if the EGR is working?
-Engine temp gauge is a lil on the high side(lil over half way up) but i think its just the wacky gauge, no overheating problems or nothing.-Don't think i'm running too rich or too lean, spark plugs don't look too bad. -Base timing is on spec 20 degrees.
Thanks on any input.
Failed emissions, help with NOx
-
racin-type
- Posts: 277
- Joined: Mon Aug 11, 2003 5:20 pm
- Car: cars
Re: Failed emissions, help with NOx (racin-type)
Well I think that you would have to be running rich if your nox is too high and your running too hot...it could be your egr valve but it could also be an oxygen sensor check those out and let me know what you found. It may also be the air metering device....
Re: Failed emissions, help with NOx (dave022)
I SAID RICH I MEANT LEAN....haha sorry dude
Re: (240kid)
I do agree with 240, you should scan the pcm for faults (continuous and hard) then mabye you could get a little better understanding of what the deal is. But why would your nox be double and hc just slightly over...let me know what you found...w0rd
-
s13sr20chris
- Posts: 4148
- Joined: Tue Jun 10, 2003 9:32 am
- Car: '89 Nissan S13 w/redtop running 13psi and not leaking fuel anymore
- Contact:
Re: (dave022)
hmmm, could be an old cat or funky o2. that sort of thing will give hc issues. so many possibilities, check codes. for nox you are def looking at some sort of egr issue. try activating the egr valve with a vac pump or engine vac to be sure it works. then be sure the bpt and egr solenoid are passing the vac along to the valve. check the hose on the bpt valve and the tube the hose is on for clogging. if all else fails retard your timing by like 5 degrees and pour in a gallon of denatured alcohol. i dont live in a smog state so i have no problem reccomending that kind of ghetto stuff to pass smog.
-
Nismo_Freak
- Posts: 10314
- Joined: Wed Jul 24, 2002 10:42 pm
- Car: 89 Nissan 240SX
Re: (NISTECH)
With the factory EGR pick-up point in the exhaust manifold I don't think the exhaust would affect the EGR operation because there is still alot of pressure built up before the catalyst due to the runner design.NISTECH wrote:your egr may not be working cause you have a high flow exhuast that has little back pressure hence the Back Pressure Transducer(BPT) wont close its internal vent to send the vaccum to the egr valve under load.
Just my .02
I'd vote funky catalytic converter... mainly because NOx production usually indicates excessively lean conditions or advanced timing due to the increased latent heat of combustion allowing the nitrogen to bond to elemental oxygen. However since you seem to be running rich due to the production of HC's it contradicts the NOx production.
Does the 5-gas report show abnormally high amounts of CO2? If this were the case then you can definately rule out a rich situation as the higher combustion temps and resulting lack of elemental oxygen tends to facilitate the production of CO.
Correct me if I am incorrect.
on the back presure issue, even the factory muffler provides some of the back pressure in the system. back pressure in the system is only about 1 to 1.5 psi to make the bpt close. you drop that number down below 1 psi and the system does not work.
On the production of NOx. If a car is running rich the excess fuel will tend to drop the knox as it cools the cyl below the 2500 degree temp needed to form the NOx.
HC does not indicate a rich mixture, CO does. but you will tend to have high HC in combination with a high CO measurement. I am not in disagreement though that the cat is done doin its job. I suspect it has become weak since all 3 readings are above limits. but since the HC is only slightly high I dont think a lean condition is causeing the high NOx. A lean condition(high HC without high CO) Will bring the cyl temp up increasing the possibility of NOx formation. In this case I do think theres a combination of things goin on 1 the egr is not functioning properly and 2 the cats rodium and paladium beds are plugged or melted and can not seperate the O2 from the nitrogen in the rhodium bed and collect it in the paladium bed to add it to the Hc to make it H2O and add it to the CO to make CO2.
CO2 is used as an indication to how effecint the combustion and cat process is in an engine. on dyno testing 14.5 to 15% is a good indication every thing is doin pretty good. In perfect combustion you should get about 1 gallon of H2O for every 13 gallons of fuel burnt.
On the production of NOx. If a car is running rich the excess fuel will tend to drop the knox as it cools the cyl below the 2500 degree temp needed to form the NOx.
HC does not indicate a rich mixture, CO does. but you will tend to have high HC in combination with a high CO measurement. I am not in disagreement though that the cat is done doin its job. I suspect it has become weak since all 3 readings are above limits. but since the HC is only slightly high I dont think a lean condition is causeing the high NOx. A lean condition(high HC without high CO) Will bring the cyl temp up increasing the possibility of NOx formation. In this case I do think theres a combination of things goin on 1 the egr is not functioning properly and 2 the cats rodium and paladium beds are plugged or melted and can not seperate the O2 from the nitrogen in the rhodium bed and collect it in the paladium bed to add it to the Hc to make it H2O and add it to the CO to make CO2.
CO2 is used as an indication to how effecint the combustion and cat process is in an engine. on dyno testing 14.5 to 15% is a good indication every thing is doin pretty good. In perfect combustion you should get about 1 gallon of H2O for every 13 gallons of fuel burnt.
-
racin-type
- Posts: 277
- Joined: Mon Aug 11, 2003 5:20 pm
- Car: cars
You guys are great. I was thinking along the same lines of thought bout the contradictory signs of the gases. However i had kinda forgotten about the cat issue.
When i bought the car, the idiot light did come on. Checked the codes and it was for the cat. Tried checking it using the fsm method by using the ratio of voltages between front and rear o2's but the voltages fluxed too much.
So now i'm definate its the cat converter. Car runs great, starts great, idles good unless i put a load on it then it starts to jump up and down.
Anyone here can recommend an OEM type replacement cat for this car?
Thanks alot.
When i bought the car, the idiot light did come on. Checked the codes and it was for the cat. Tried checking it using the fsm method by using the ratio of voltages between front and rear o2's but the voltages fluxed too much.
So now i'm definate its the cat converter. Car runs great, starts great, idles good unless i put a load on it then it starts to jump up and down.
Anyone here can recommend an OEM type replacement cat for this car?
Thanks alot.
-
racin-type
- Posts: 277
- Joined: Mon Aug 11, 2003 5:20 pm
- Car: cars
Re: (racin-type)
Forgive me if I'm wrong, but don't 95s have 2 O2 sensors and 96s have 3? A regular cat shouldn't cost an arm and leg anyway.racin-type wrote:You guys think i can use a cat from another s14 instead of buying one? Will a cat from a 96 fit on a 95 and will the second o2 sensors fit vice versa? thanks
on the CA edition sentra [which btw doesnt mean california it means clean air] They had 4 o2's one for exaust runners 1and3 and one for exhaust runners 2 and 4. this help better fine tune the mixture for better emissions control, the one cat unit mounted to the manifold actually has 2 seperate cats with in it. This car ran so clean it actually cleaned the air going through it, what came out the back of the car was cleaner then the air in front of it. It was short lived though as the expense to make this car made the car not all that profitable cause after all it was a base line sentra. It had a cataylist radiator which runs about 7 bills.
-
racin-type
- Posts: 277
- Joined: Mon Aug 11, 2003 5:20 pm
- Car: cars
finally went back to take the emissions and passed with flyin colors.
used my friends exhuast from the cat back. while doing that saw that my damn exhaust did not have a cat where it should, just the second resonator cat. in place was a ugly welded crushed bent pipe.
No wonder i didn't pass and figured out where my exhaust leak was. so thanks again
used my friends exhuast from the cat back. while doing that saw that my damn exhaust did not have a cat where it should, just the second resonator cat. in place was a ugly welded crushed bent pipe.
No wonder i didn't pass and figured out where my exhaust leak was. so thanks again