95 honda civic won't pass emissions

I've had my honda civic's emission system tested three times and it failed
three times. I've changed the spark plugs, oil, wires, distributor cap,
rotor, o2 sensor, and the air filter. Does anyone have any suggestions on
what else needs to be done? The reading for the last test on HC was 224
with the allowed being 147, CO reading was 2.10 with the allowed being
0.82, and the NO reading was 1825, with the allowed being 1072. All of
these readings were done on the 25/25 test. On the 50/15 test, the
reading for HC was 195 with the allowed being 152, CO was 1.48 with
allowed being 0.85, and the NO was 1808 with allowed being 1186. I just
changed the oxygen sensor but I don't want to have it tested if there are
other things that needs replacement as well. Any help is appreciated.

 

What were the readings for O2? I know there is no pass / fail for O2,
but it is valuable to know for diagnostic purposes.

If there is plenty of O2 in the exhaust, it would seem your catalytic
converter is not doing its job.

 

++++++++++++++++

You didn't mention changing your PCV . . . Very easy to do on most
Hondas, and often overlooked when mileage suddenly goes down the toilet,
or oil consumption rises.

Do a google search to learn more.

'Curly'

 

I think the O2 reading on the 25/25 test was 16.1 and on the 50/15 test it
showed 15.9 with the allowable on both being 6.0.

 

Thanks, I'll check into that.

 

Thanks,I'll check into that

 

sounds like youve done everything but the catalyst. make sure the timing
is set to spec too, and id check the valve clearance. a compression
check would also be handy, to see how the rings and everything else are.

 

You need a catalytic converter.

 

16% would be VERY high for O2. are you sure it is O2 and not CO2 that is
16%

 

That was my error on the previous post. The CO2 reading is 16.1 on the
25/25 test and 15.9 on the 15.9 test not the O2 reading

 

a new cat would take care of all 3 pollutants. but if the car isnt tuned
right, the new cat might not last long.

 

Which is why it would be interesting to se the O2 numbers. If there is
plenty of O2 in the exhaust, I would agree that a new cat would solve
the problem. If there is next to no O2 in the exhaust, a new cat would
do nothing.

 

Dear Curly,

This is a common problem for all civics. NO emmission or called as
"No-x" by all auto technicians. I also had an 89 civic with 150000
miles. Awsome near car, no dents, no probs, good milege 35 m/gall..
why would some one sell one ?

Last year there comes a test only from dept of motor vehicles, Ca
which made me think twice before going for smog. I did all check lists
before smog and it failed for smog. NOX - 10 points above .

Honda Techs here in sacto adviced me to do 150000 mi serv. $380.00
gone came again with same reading.

Then was the tune up and so on final result $1000 + fail
I had to then sell this car to a dealer

If you live near foot hills, NOx emissions are not reguired by law.
Drive down and check smog places. If you are in ca, i could advice
some

 

on a scale of?

well, yeah. did that include a new O2 sensor? after 150k miles, the cat
might very well be shot.

at gunpoint? could you have gotten an aftermarket cat for it?