92 Accord failed emission with high NO
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92 Accord failed emission with high NO
My 92 Accord DX just failed emissions with high NO at 15 MPH, everything else is fine.
Here are the numbers:
-----------RPM CO2 O2 HC CO% NO
15 MPH 1846 14.3 0.2 85 0.36 967 (MAX is 791)
25 MPH 2559 14.4 0.1 51 0.21 366
Does the CO2 numbers mean it's running rich or lean? Should it be 14.7? Any ideas on what to do to get it to pass? Any help will be much appreciated. In case it matters, it has DC Sports headers, not sure if that effects smog in any way.
THanks in advance!
Here are the numbers:
-----------RPM CO2 O2 HC CO% NO
15 MPH 1846 14.3 0.2 85 0.36 967 (MAX is 791)
25 MPH 2559 14.4 0.1 51 0.21 366
Does the CO2 numbers mean it's running rich or lean? Should it be 14.7? Any ideas on what to do to get it to pass? Any help will be much appreciated. In case it matters, it has DC Sports headers, not sure if that effects smog in any way.
THanks in advance!
Last edited by Conan; Apr 3, 2009 at 04:25 PM. Reason: added header info
Junior Member
Joined: Mar 2007
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From: Osaka, Japan
Re: 92 Accord failed emission with high NO
OXIDES OF NITROGEN (NOx)
There is little the mechanic can do to control NOX emissions, except to make sure the engine and E.G.R. valve (on vehicles so equipped) are functioning properly.
One of the keys to emission control techniques is controlling the air/fuel ratio. The point at which the A/F mixture burns efficiently for peak catalytic converter operation is called the Stoichiometric Point or ideal air/fuel mixture. At this point the HC, CO, O2 is near peak. The point at which complete combustion occurs is 14.7 to 1A/F ratio (called "Theoretically ideal").
High NOx on driving Test
- Inoperative or ineffective EGR (Exhaust Gas Recirculation) system
- Excessive lean air/fuel ratio
- Inoperative or missing catalytic converter (three way catalytic)
- Excessive spark advance
- Faulty Thermostatic Air Cleaner (TAC) system
- Defective computerized engine management and/or Oxygen sensor
- Engine Deposits (Carbon)
- Engine Mechanical defect(s)
http://www.troublecodes.net/articles/smog.shtml
I would suggest that the EGR system be checked FIRST; with the engine at idle put your finger under the lid of the EGR valve and 'manually' lift the pintle. The engine should stall or stumble badly. If not the EGR ports need cleaned.
NOX is the catchall name for a group of chemicals of different Nitrogen and Oxygen combinations. When enough NOx is present in the air combined with sunlight forms irritating smog when mixed other elements in the air.
Nitrogen (N) makes up approximately 78% of the air we breath and the rest, approximately 21% is oxygen. The engines in today's vehicles use oxygen to operate and exhausts the nitrogen. NOx is formed when the combustion temperature exceeds 2500° F.
Unfortunately an engine designed and tuned to produce low CO and HC produces high NOx The hotter an engine runs the more power it delivers, the more NOx it produces.
Late Model vehicles operate with a very lean A/F mixture so the NOx is very high and a "three way Catalyst is incorporated converting CO, HC and NOx.
A device called the E.G. (Exhaust Gas Recirculation) Valve was designed to lower the combustion temperatures by recirculating exhaust gasses back into the combustion chamber.
NOTE:Nitrogen (N) makes up approximately 78% of the air we breath and the rest, approximately 21% is oxygen. The engines in today's vehicles use oxygen to operate and exhausts the nitrogen. NOx is formed when the combustion temperature exceeds 2500° F.
Unfortunately an engine designed and tuned to produce low CO and HC produces high NOx The hotter an engine runs the more power it delivers, the more NOx it produces.
Late Model vehicles operate with a very lean A/F mixture so the NOx is very high and a "three way Catalyst is incorporated converting CO, HC and NOx.
A device called the E.G. (Exhaust Gas Recirculation) Valve was designed to lower the combustion temperatures by recirculating exhaust gasses back into the combustion chamber.
There is little the mechanic can do to control NOX emissions, except to make sure the engine and E.G.R. valve (on vehicles so equipped) are functioning properly.
One of the keys to emission control techniques is controlling the air/fuel ratio. The point at which the A/F mixture burns efficiently for peak catalytic converter operation is called the Stoichiometric Point or ideal air/fuel mixture. At this point the HC, CO, O2 is near peak. The point at which complete combustion occurs is 14.7 to 1A/F ratio (called "Theoretically ideal").
High NOx on driving Test
- Inoperative or ineffective EGR (Exhaust Gas Recirculation) system
- Excessive lean air/fuel ratio
- Inoperative or missing catalytic converter (three way catalytic)
- Excessive spark advance
- Faulty Thermostatic Air Cleaner (TAC) system
- Defective computerized engine management and/or Oxygen sensor
- Engine Deposits (Carbon)
- Engine Mechanical defect(s)
http://www.troublecodes.net/articles/smog.shtml
I would suggest that the EGR system be checked FIRST; with the engine at idle put your finger under the lid of the EGR valve and 'manually' lift the pintle. The engine should stall or stumble badly. If not the EGR ports need cleaned.
Thread Starter
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Re: 92 Accord failed emission with high NO
Thanks for the info guys. I checked the EGR, it definitely stalls the car to move it. I used the Chiltons to test the O2 sensor, and it had no output. I picked up a new O2 sensor. I think I am going to replace the O2 sensor and the cat conv. I just want to make sure it will pass before I take it back. Thanks again.
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thandaman22
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Dec 1, 2012 05:47 PM
