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Discussion Starter · #1 ·
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?
 

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Discussion Starter · #3 ·
lshadoff said:
Nitrogen oxides are controlled by the EGR system. Make sure yours is functioning correctly.

Lew

how do i check this. ive already replaced all of the hoses, and the diaphram moves easily.
 

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I found this in the B13 Factory Service Manual:

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.

Lew
 

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Also have high NOx

OK, I'm suffering from the same symptoms of failing emissions and because of high NOx. Where is EGR valve located to perform these tests?

Thanks,
Ron
 

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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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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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Discussion Starter · #8 ·
bahearn said:
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.
 

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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
 

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BrookShadowRC said:
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.
 

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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?

Again, thanks a ton in advance for the help,
Ron
 

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The fact you failed multiple portions of the test leads me to think you need a new catalytic converter.
 

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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.

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.
 

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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.
 

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Narrowed it down...

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?

Again, thanks for the help.
Ron
 

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IGNITION TIMING


1. Start the engine and warm it up until the water temperature indicator points to the middle of the gauge.
2. Operate the engine at 2000 rpm for 2 minutes under no load.
3. Disconnect the throttle sensor connector.
4. Idle engine and check timing. Timing should be 10°±2°BTDC. If not, proceed to step 5.
5. Idle engine and adjust the ignition timing to 10°±2°BTDC by turning the distributor after loosening the securing bolt.
6. Turn the engine off.
6. Reconnect the throttle sensor connector.

Actually, the info from Alldata ^ seems to not be as detailed as these other references.

http://www.nissanperformancemag.com...98/timing.shtml

http://www.g20.net/forum/showthread...&threadid=13470
 

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Highway Robbery!

Well, I just called my local dealer to see how much the cost of replacing the EGR valve would be... $500.00! So, I think that today, I will go to O'Reilly and get the part for $100.00 and install it. Then we will see how emissions go...

Ron
 

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Ron, PM me before Friday. I'll be in your neck of the "woods" and can stop by with my factory service manual.
 

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Upon closer inspection yesterday, there was oil in the distributer cap. So I replaced it and added some water to the radiator. Went back this morning and failed again on emissions, but the numbers were better:
HC down from 189 to 186
NOx down from 2728 to 1972

I have a sinking feeling in my check book this is going to cost me BIG time...
 

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Don't mean to hijack the thread...

I also failed emissions and my NOx levels were in the 2500 range. My compression is fine though. I have a '94 Sentra with a stock CAD converter but my oil filter hasn't been replaced in a long time either, I've had the car a year now and I haven't had it replaced (stupid I know) and I don't know how long before I owned it, that it last saw a replacement. I've also been reading on this forum that it's also highly likely that my EGR valve is plugged or gone entirely (the car has 186k miles), how easy is that to replace if I need it to? I was thinking about dumping some BG 44k in my tank to see what that does, but given the high level of NOx I have a feeling it won't do it enough.

Mind you, when I had the car tested, I didn't drive it a long time beforehand. I drove it maybe 5 minutes and it wasn't highway driving.

Any help would be appreciated guys, thanks!
 
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