Always good to see these reports. I make a mental note and then often
end up groups.google searching for some of Tegger's updates somewhere
down the line.
One interesting point to me: His Integra is passing smog with an 8-
year-old, 146k miles O2 sensor. I had almost talked myself into
replacing these every 50k miles, based on some suspicions on why my 91
Civic a few months ago could not get past smog.
honda.lioness@gmail.com wrote in news:d4509dc8-19af-420f-9ccf-
acdda05ea5de@g19g2000vbi.googlegroups.com:
> Always good to see these reports. I make a mental note and then often
> end up groups.google searching for some of Tegger's updates somewhere
> down the line.
>
> One interesting point to me: His Integra is passing smog with an 8-
> year-old, 146k miles O2 sensor.
This was interesting to me as well because I did have considerable concern
about the oxygen sensor before this test.
The original sensor was replaced on account of the Check Engine light
having come on twice with a Code 1 in the months before the first test.
The current replacement sensor has not yet tripped any codes, but it's
getting very close to the mileage where the original sensor began to give
trouble.
Maybe Denso has improved their sensors since 1991. And maybe the newer
gasoline is formulated to be kinder to oxygen sensors. The original sensor
spent all of its life in the presence of MMT, which can cause deposits on
certain emissions control hardware. The new sensor has seen little MMT.
> I had almost talked myself into
> replacing these every 50k miles, based on some suspicions on why my 91
> Civic a few months ago could not get past smog.
I've seen numerous recommendations both on and off-line that sensors should
be replaced every 60K as a matter of course. But at over $300 for new OEM
Denso, it seems to me that ours ought to last quite a lot longer than 60K.
And it seems like they do exceed that figure by a considerable distance.
Did you ever post your numbers when the Civic wouldn't pass?

Signature
Tegger
The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/
honda.lioness@gmail.com - 12 May 2009 13:53 GMT
> I've seen numerous recommendations both on and off-line that sensors should
> be replaced every 60K as a matter of course. But at over $300 for new OEM
> Denso, it seems to me that ours ought to last quite a lot longer than 60K.
For my 91 Civic and now 93 Civic, I can get the new OEM Denso oxygen
sensor through Amazon for about $30. www.densoproducts.com is almost
as competitive.
> And it seems like they do exceed that figure by a considerable distance.
>
> Did you ever post your numbers when the Civic wouldn't pass?
No. I had it tested several times. Mostly it failed at idle but not at
high speed. The last reading before I sold my 91 Civic (to people
living in a no emissions testing required county):
Failed idle with
HC = 460 (limit is 180)
CO = 1.8 (limit is 1.2)
My last theory is that I had air leaks at the throttle body gasket
(you could hear them using some Tygon tubing as a stethoscope). A
little Hondabond sealant fixed this. But I think the air leaks may
have resulted in rich running for so long that the O2 sensor was
fouled. I did some checking of the O2 sensor and it was not bouncing
around 0.45 volts the way certain web sites said it should. So my next
step would have been to put in a new O2 sensor. If a new sensor would
not fix it, then I think I would have done a compression test and seen
if the engine was just too old and worn to pass emissions. Miles per
gallon was still pretty good when I sold it, so it is hard to say.
At honda-tech.com I think the threads that are left unresolved most
often are the smog ones for the older Hondas.