nox emissions are to high

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eric4321
Posts: 143
Joined: Wed Mar 31, 2010 11:14 pm
What year is your cabby?: 1993
Do you own a Cabriolet?: Yes
Location: Atlanta, GA

nox emissions are to high

Post by eric4321 »

Well it is that time of year again. Had to get the Cabby to pass the GA smog test. For some reason the nox reading is sky high. Last year the shop retarded the igniton timing and it passed. Well being as cheap as I am I marked whare they set the timing so I would not need to pay them again. It turns out they set the base timing to several degrees after TDC. The car runs like junk and has no power but passes smog. Well I would like to figure out why the nox is so high when base timing is set to specs. The research I have done makes me think the o2 sensor may be causing it to run to lean. Just wondering if anyone knows a way to check it. I don't have a gas analizer which is what Bentley says you need. Also could the mass air flow sensor be causing a lean condition? I got the car to pass by retarding the timing again but I would like to figure out what the cause of the high nox is.
My Rabbit Rescue and Recovery Ranch
93 Cabriolet red. 5 speed
81 Rabbit 4 door auto bronze (project)
77 Rabbit 4 dr 4spd diesel
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kamzcab86
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Re: nox emissions are to high

Post by kamzcab86 »

Running too lean (high combustion temps) due to:

* Vacuum leak(s)
* High idle due to vacuum leak
* Faulty/clogged catalytic converter
* Faulty oxygen sensor
* Timing is advanced too far
* Incorrect air-fuel mixture
* Dirty air filter
* Faulty ignition components

If the car is CIS, get your duty cycle/dwell meter out and check the readings; make adjustments as needed: http://www.cabby-info.com/cis .

:beer:
eric4321
Posts: 143
Joined: Wed Mar 31, 2010 11:14 pm
What year is your cabby?: 1993
Do you own a Cabriolet?: Yes
Location: Atlanta, GA

Re: nox emissions are to high

Post by eric4321 »

Thanks for the info Kammy. My Cabby is digi not cis. I have set the timing folwing Mr Bentley, the cat is less than a year old and the idle speed is ok. I am going to recheck for vacume leaks but the car runs great and does not show any signs of vacume leaks. I will go ahead and shell out for the new 02 sensor soon.
My Rabbit Rescue and Recovery Ranch
93 Cabriolet red. 5 speed
81 Rabbit 4 door auto bronze (project)
77 Rabbit 4 dr 4spd diesel
(Project next in line)
1987 Cabriolet parts car(may one day bring her back)
1993 Suburban green(used for Rabbit rescue)
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Briano1234
Whats that smell?
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Joined: Mon Mar 21, 2005 5:45 am
What year is your cabby?: 1992
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Location: Duluth, Ga
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Re: nox emissions are to high

Post by Briano1234 »

eric4321 wrote:Thanks for the info Kammy. My Cabby is digi not cis. I have set the timing folwing Mr Bentley, the cat is less than a year old and the idle speed is ok. I am going to recheck for vacume leaks but the car runs great and does not show any signs of vacume leaks. I will go ahead and shell out for the new 02 sensor soon.
I have the same issues with mine. Replaced the cat and o2, hoping that I pass this year.
Briano

Yes as matter of fact, I have the Luck o'the Irish...everything I touch turns to fertilizer of the bovine variety.
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kamzcab86
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Re: nox emissions are to high

Post by kamzcab86 »

eric4321 wrote:Thanks for the info Kammy. My Cabby is digi not cis. I have set the timing folwing Mr Bentley, the cat is less than a year old and the idle speed is ok. I am going to recheck for vacume leaks but the car runs great and does not show any signs of vacume leaks. I will go ahead and shell out for the new 02 sensor soon.
Yeah, I saw it was a '93 after I posted. :oops: But I figured that if someone searches and has CIS, it may help, so I left it.

I have the displeasure of smogging my '86 next month, but she has CIS so I can check her air-fuel ratio and make minor tweaks, if need be. :mrgreen:
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gull
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Re: nox emissions are to high

Post by gull »

Is the NOx too high at idle, under load, or both? That might be a clue to where the problem is.
VW fan who fell to the Honda side of the force
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