What causes an 1982 Honda Accord not to pass smog because of NOx?
if car is properly tuned . most likely cause would be catalytic
The existing answer if very likely the most accurate however, NOx
is caused by excessive heat. Perhaps the fuel/air mixture is not to
spec. It also may be due to a fouled combustion chamber due to
carbon build-up. A fuel additive may be a simpler and less
expensive solution. Certainly worth the try.
You will want a good cleaning additive, however, you must be
careful because cleaning additives may also increase the heat and
make matters worse.
With any additive you should drive through a full tank of
treated fuel to get the best results.
I've read on the web about many such additives. STP, Techron and
the like. There is also one that seems to get good reports, at
least according to its website. It isn't widely available in
stores...again according to its website. I think it is called
BlueSky 3-in-1 Fuel Conditioner. Any one would probably do the
trick. good luck.