1G High NOx at 15mph only (CA smog)

[Shinotheweevil]

Hey guys,
I need help with my smog. I went to go smog it and it only fails NOx at 15 mph. But at 20mph it passes with flying colors which the smog guy says its very weird that its in two different extremes. Im going to check base timing and my egr when I get a chance, but is there another thing that I missed?
1990 eclipse gs-t and mods are FMIC and exhaust other than that it is stock.

Thanks guys

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[danl]

Are you able to check the air/fuel ratio with a wideband at 1700 rpm/15 mph to see if it is off? Since it is fine at higher rpm/speed, I would focus on things that can vary due to engine speed. O2 would be the first thing I would check.

 

[Shinotheweevil]

Sadly I don't have a wideband. I should look up in how to get one installed. But I'll keep you updated. Thanks!

 

[Dhan]

A wideband would help, because then you could see what air/fuel ratio you're running at.

But even without a wideband, we can tell you're running lean, because your NOx is high. If it were me, I'd try and track down any vacuum leaks and check my EGR. Once you're 100% positive there's no vacuum leaks, remove and clean the EGR. Use carb cleaner spray and brushes. Make that thing sparkle on the inside. Use a pick to remove the old carbon.

 

[awdmonster1904]

If you get tired of the smog send me a PM