89 Honda Civic fails new smog test; NOx @25mph

Ahoy.

I'd appreciate a quick word of advice. My 89 Honda Civic LX just failed the CA smog test. Everything was fine--inclucing the 15MPH dyno test on NOx, but at 25MPH, it failed causing me to fail the test.

It was reading 927 with a max of 798 allowed. So it was kinda close, but failed. (the 15MPH test just *barely* passed btw...).

What should I check? I turned down their $100 diagnosis fee...figuring then they'd add another big chunk to fix something that might be simple.

Would one of those "pass smog test guaranteed" additives help? Is there some some particular gas/oil additive that might help? Something else? I'm hoping some kind of emissions reducer might help me avoid a big bucks "fix."

I'm bummed; nearly broke and not a ton of $$$ to contribute to fixing a few ppm of NOx....

Thanks in advance,

Tom

Reply to
Tom
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NOx is usually the EGR valve or thermostat not opening up. NOx is formed when the engine gets very hot.

Don't bother with any additives, it won't help.

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Reply to
Barry S.

First thing to check is that the EGR is working properly (valve opening properly, and passages not clogged with carbon). Also check that the ignition timing is correct. If those are OK, then the most likely cause is that the catalytic converter is worn out.

Reply to
Robert Hancock

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