gutzguy

well i took my car for emission test and it failed. the test said the no ppm limit is 408 my car is reading 1157ppm any ideas as to why reading is so high

maxwedge

Welcome to AF, NOX, I assume is what you are referring to? Inop egr if equipped is number one, number 2 is a bad cat and very high engine temps is number 3.

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HotZ28

WHAT IS NOx?
Nitrogen and oxygen naturally coexist in the atmosphere. At temperatures above 2500 degrees Fahrenheit (which occurs in the combustion chamber), they chemically combine to form NO, NO2, and NO3 – also known as NOx, which is a corrosive gas.
In addition to the items mentioned by Max, some other possible causes of excessive NOx include:
• Incorrect ignition timing
• Incorrect fuel pressure
• Broken or leaky vacuum hose
• Faulty mass air flow sensor
• Faulty or malfunctioning thermostat
• Old coolant / antifreeze
• Faulty oxygen sensor(s)

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gutzguy

thanks for your help i will try the EGR first maybe just a ceaning will help

spinne1

Well, it is an urban legend (I don't know if it is true or not!) to take your car on the interstate right before emissions testing and really ride it hard for about 10 miles or so (go about 80-90 mph if you can get away with it) and "blow out" the cat. I always do it because my two LeSabres are old. However, after recently rebuilding my two engines in the past year my testing has gone extremely well. After testing my wife's car with 197K (but newly rebuilt engine) the testing guys seemed surprised at how low my numbers were because of my mileage. One number was like 14 ppm with a max allowed of 220 and the other was 0. The other car had similar numbers but lower.