Hi my accord just failed emission test in MA, high NOX level. Any ideas on ther cause/solutions? car has never failed before and has 160,000 miles. Would like to fix myself.

thanks,

Mike

 

almost positive its "blocked EGR ports". See my sig below for the DIY.

maybe ~$120 to get them cleaned by a shop. Shop around.

 

I probably should have also mentioned that it aso periodically idles high for no reason, the back to normal. Does this sound like a vacuum leak? I understand this can also increase NoX. I read the post on cleaning ERG, but it seemed only to mention the 93's that need "surgery" to create access. Do I need to remove fuel lines and depressureize the system?

Thanks,

Mike

 

Yea I would say EGR as well. Here is a decent article you may want to browse:

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by smog definitions &raquo;</TD></TR><TR><TD CLASS="quote">3. OXIDES OF NITROGEN (NOx)

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:
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").

These three gases are what are looked at when an emission test is done and considered the most polluting.</TD></TR></TABLE>

From: http://www.troublecodes.net/articles/smog.shtml .

As for the idle going up and down periodically I would suggest looking at your vacuum lines along with your fast idle valve or IACV (intake air control vavle) here is a DIY from another website: http://www.cb7tuner.com/vbb/showthread.php?t=12106 (that may provide some help) . And this one: http://www.cb7tuner.com/vbb/showthread.php?t=567

 

Thanks Ken,

Can a bad thermostat also contribute to this? I thought Mine was sticking open becuase I have poor heat in winter - but perhaps not.

Mike

 

I doubt a thermostat would cause that, honestly your car isn't warming up "properly" and that may cause not good heat. I would fix this problem first and go from there .