i have a 93 se-r that has 126k on it. i cant pass emissions because the nox level is double what its supposed to be. my compression is also going bad. last time i checked it was about 115 on all four. would it just be my catylitic converter?
1989-95 ENGINE PERFORMANCE
Nissan EGR Function Testing
All Models
EGR VALVE
1) Disconnect vacuum hose to EGR valve. Plug end of
disconnected hose. Connect a vacuum pump to EGR valve. With engine
idling, apply vacuum to EGR valve. If vacuum holds and idle becomes
unstable or engine stalls, EGR valve is functioning properly.
2) Ensure engine is at normal operating temperature. Connect
a vacuum gauge to EGR hose. Increase engine speed to about 3000 RPM.
If vacuum is shown on gauge, system is functioning properly.
Your EGR may need a good cleaning if it is not working properly. I removed mine recently to clean it. There was a carbon build up around the pintle. It is located in the area below the throttle body on a 1.6. It is bolted onto the lower intake. Some people say it looks like a flying saucer. You will see a vacuum hose coming out of the top. There is a large metal pipe from the exhaust manifold attached to the bottom of the EGR.
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Last edited by Catman : Apr 7th, 2005 at 11:15 AM.
The catalytic converter also affects NOx emissions. After you've verified proper operation of the EGR system (don't forget that tiny pipe that easily clogs with carbon), and if you still fail the test, replace the cat.
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Bruce in Houston
'94 Nissan Sentra SE-R w/ $tuff, converting to ITA
'98 Suzuki Bandit 1200S w/ $tuff
'02 Dodge Dakota SLT 4-dr tow beast, stock!
The catalytic converter also affects NOx emissions. After you've verified proper operation of the EGR system (don't forget that tiny pipe that easily clogs with carbon), and if you still fail the test, replace the cat.
ok i checked the egr valve and all of the hoses and tubes. they were all good. my cat is still the origional one with 126000miles on it so that would be my next guess. is there any thing else that could also cause this?
thanks in advance.
What about O2 sensor? I seem to remember the Nissan dealer saying that this might also need replacing if emissions continue to be high? Any thoughts?
Ron
Only if you fail the HC or CO portion of the test. NOx is affected by EGR, cat or timing. You could try retarding timing a couple of degrees to cool combustion temps a smidge.
__________________
Bruce in Houston
'94 Nissan Sentra SE-R w/ $tuff, converting to ITA
'98 Suzuki Bandit 1200S w/ $tuff
'02 Dodge Dakota SLT 4-dr tow beast, stock!
As a matter of fact, I failed both HC and NOx at the low speed (15mph) test. At the 25mph test, I passed on all accounts. Does this mean I need EGR, O2, and timing? Or is there one item that will cause the rest in a domino effect?
ok i checked the egr valve and all of the hoses and tubes. they were all good.
Did you actually test the EGR with a vacuum pump and vacuum gauge like Lew posted? I say this because I cleaned my EGR since I was getting pre-ignition/pinging at very light throttle. Everything I read said it was caused by the EGR not working properly. The whole idea is combustion temperatures get too high, NOx increases. Also, advancing the timing could contribute. I even changed my thermostat to the OEM 170 degree temperature, from the 180 degree one I replaced a while back. So, there is a domino effect. Things that increase combustion temperatures increase NOx.
Quote:
After you've verified proper operation of the EGR system (don't forget that tiny pipe that easily clogs with carbon)
I am curious about the tiny pipe that easily clogs. It's specific location would be nice to know.
A Bosch O2 sensor I bought at Auto Zone was only about $35.00 and seemed to work OK. Since it was $75.00 to have diagnostics done when I failed emissions, I just did a tune-up, had injectors cleaned, and replaced the O2 sensor. Passed with flying colors, but don't remember which areas failed.
__________________
Truth alone triumphs, not untruth. :)
I had the same problem with my car, it turns out that the oil on K&N air filter, if too much oil, will get on the MAF and cause it to misread the correct volume of air. To clean it use a brake parts cleaner that has no oil in it and spray it clean. To test it, just spary it on a finger and if your finger turns white as the fluid dries it will be the correct one. I put in a paper filter after cleaning the MAF and then retested the system and it passed better then it was new, car had 177,000 miles on when this was done.
At this point, I'm leaning to the EGR. I cannot test, because I don't have the equipment, but I was looking at last years emissions results. NOx went from a reading of 780 last year to 2728. The O2 sensor was replaced 3 years ago. The air filter is still paper and changed a month or so ago. During this last year, I started using premium gasolone to reduce knocking and pinging, and started driving around town a lot more.
I do still have another questions about adjusting timing, like what are the steps to adjust it? Does it require popping the distributer cap?
Linear Mode
