Activ1

My brother has a 1993 Sc400, this is the third time it has not passed emissions (Maryland). Originally it was a North Carolina car, and my brother had it pass Maryland emissions a few years ago.

The 1st time it failed, it was the Nitrogen oxide that failed by small amount. My dad and brother changed the spark plugs, but these were pre-set, and not gapped for the SC400, it took it and all the categories jumped up, but it was still the Nitrogen Oxide. They regapped the spark plugs, and my bro still failed, but the Nitrogen Oxide was lower...

What could be the cause of the Nitrogen Oxide Level being higher...

That's for your help,

Forum newbie

RolxuSC400

Could the o2 sensors be causing this?

cbrasian

egrsystem or bad 02 sensor or bad cat you need to test each system to figure it out

Activ1

Don't know, my brother hasn't changed them. Could asking the Lexus dealership the reason why the Nitrogen Oxide is higher, and it has failed?

Activ1

Thanks, I'll have my brother take it to a place to get it checked out....