audi 100 fails smog NO test

[wpatters1229]

The audio 100 v6 had 203 k but two years ago I had both caytalitc converters replaced and the NO levels where both around 49 way below the 700 which is the high level in CA.
Now two years later everything else in the test was exactly the same but the NO levels are now above the max level around 750. What could be the problem?
I have heard the things to do is replace the air cleaner, get some of that "guarentee to pass" gas additive etc. I have replace the plugs and new wires. It uses a magneto so there is no distributor to mess with.

Not sure about NO sensors or Oxygen sensors. It has about 203 k miles but runs great.

Any help would be greatly appreciated. [email protected]

Thanks

[wpatters1229]

In another forum someone said that it sounded like the EGR valve might be the problem. How can you check that and where is it located on this v6 engine?

Thanks

[nicke66]

Originally Posted by wpatters1229

In another forum someone said that it sounded like the EGR valve might be the problem. How can you check that and where is it located on this v6 engine?

Thanks

The EGR valve is located in a bypass line from the exhaust to the intake. It is regulated with vacuum. The valve use to get stucked and need to been cleaned.