high NoX, no pass emissions

[deadhooker]

Hi All,

I've got a 91 Civic that I believe has the stock motor. It has now failed emissions twice, both times with a high nox reading.

Any ideas on what to inspect or replace?

all new cap,rotor, plugs,wires,etc. I did a search and alot of stuff came up with possible o2 sensor. If so, which one would I inspect?

 

[Briansol]

o2 sensor is likely the cause... that or a bad cat.

 

[deadhooker]

stupid cats, this will be my 3rd in the last month (not this car, a different one).

Also, it has an engine light on. The oil light is also on, but it has good pressure and does indeed have oil. Where could I just buy an obd1 scanner?