So you get an emissions test, and the only thing that fails is your NO levels...NOx, whatever. Does that mean bad cat and/or O2?

That's what this garage is trying to say, which I thought was BS. I had learned about emissions in one of my auto classes, and I could have sworn NOx levels were from your engine burning hotter than needed, which creates the emissions they don't want. So wouldn't this be an EGR thing?

Now, let's just say the car didn't come with EGR, how would you fix this?

Would that stuff you dump in the tank help this?

Thanks guys!

 

High NOx generally means its running lean. Low HC and CO at the same time would tend to confrim that. Might also be a problem with the EGR system.

What year is your car? 4th Gens have monolithic cats, 3rd Gens require the AIR feed between the two beds in the cat.

Why not add a "signature" with basic info about your car, so people don't have to guess?

 

Actually, it's not about my car.

Sorry, it's about my girlfriends BMW...it's a '94 318is.

That's right, it's because of a lean mix. I knew I was forgeting something.

 

Are you running high octane? Higher octane will cause higher NOx levels.

NOx is a generic term for the Nitrogen and Oxygen compounds caused from using air as a source of oxygen in combustion, since air is mostly Nitrogen.