Re: emissions test failed, need ideas on reducing NOx, please

Yes. john is correct. Cats have come way down in price. It would be best to do some further testing though just in case there are other problems and the old cat is actually good. Outlet temp should be as high or higher then inlet temp. High HC as well as high NOx COULD mean bad cat. Could be other things as well. Definitely check the O2 sensors. BorgWarner sometimes has some good tech tips:

A quick test is to just run the engine without the EGR valve on it and see if a bunch of exhaust gas comes blowing out of the passage to the exhaust pipe. The real issue is the passage from the valve to the manifold, how clear is that? Without an EGR valve you should have very strong suction coming out of that passage when the car is running, of course.

A NOX reading 1 and 1/2 times higher than normal is pretty hard to reduce by just dicking with it. I think that fundamentally your engine isn't introducing enough exhaust gasses back into the manifold.

The only other rule of thumb you can try is to run the cat up as hot as it will go before the test. A cold catcon isn't as efficient.

On

replacing good catalytic converters is a favourite scam of muffler shops. they used to do it long before there was emissions testing.

converters on older cars dodn't reduce NOx emissions. mine doesn't. I think it's called a one-stage converter. Only 2-stage converters on later cars do anything to reduce NOx.

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