Hi,

I have a 1998 Integra LS.

I have failed my smog retest after running seafoam treatment and tuning the ignition system. Before I was failing based on high HC, but now I am failing on high NOx, which was passing before.

What is really weird is that the NOx measurement is all over the place.

15 mph - 1071 ppm (fail)
25 mph - 27 ppm (pass)

What could cause this drastic difference at the slow speed? I haven't changed the ATF in 40k miles, and I notice sometimes at slow speeds the transmission doesn't catch all the way and bogs down the engine. Could this have caused the smog test to fail?

I am just trying to sell the car doing the minimum amount of maintenance on it, so if the ATF needs to be changed, so be it, but I want to rule out having to do anything else before I spring for it.

Thank you for your reply

 

Does the car have EGR? It may not be getting a strong enough signal during the 15 mph test.

 

thanks for the reply. The engine is a stock B18B2 which has an EGR system. I believe now after looking up how NOx forms in the engine and how EGR works that my bog problem is causing the engine's feedback control system to go nuts, burning hotter and causing higher NOx. Does anyone agree with this?