Just passed the Cal smog test by the skin of my teeth...

Basic info: '96 Civic with 120k mostly highway miles. No oil burning
as fas as I could tell. New air and oil filters, oil, coolant, pcv,
cap, rotor and spark plugs. Tire air pressure to spec. About 20
miles to warn up car. Yet, results as follow:


HC(PPM) CO(%)
Test Max Ave Meas Max Ave Meas
M1: 15 mph 66 9 60 ! 0.57 0.02 0.45 !
M2: 25 mph 49 7 33 0.55 0.03 0.51 !

NO(PPM)
Test Max Ave Meas Result
M1: 15 mph 487 57 484 !! Pass
M2: 25 mph 774 50 31 Pass

Don't have results from prior years anymore, but don't remember
anything being that high. Mechanic said might be the catalytic
converter, but I searched the Google archive and think it may be the
O2 sensor(s) instead, based on the mileage. How is the best way to
check the O2 sensors, without a scan tool? The factory manual is not
too clear on this. Since there are two, is the front one the first
to go?

Anything else I should consider?

Any help is appreciated

 

just went through this myself, with a bad O2 sensor. they are both 4-wire
designs. the one that went bad on mine was the "top" one, in the manifold.
it threw a code P0135. seems like yours is on its way out?

if you connect an ohmmeter to the "bottom" 2 wires of the plug on the sensor
side, you can check the resistance of the heating element. should be between
15 and 40(mebbe 45) ohms.

sunno if itll help you, or if your heating element is the problem. my top
sensor read ), and the bottom read 16ohms. the replacement sensor read 16
ohms. mebbe the resistance goes up as it ages/wears?

my car is a 98 CX, with 45k miles. figured it was still in too good a shape
to be throwing aftermarket bosch stuff in there, so i sprung for the $200
OEM one. plug and play, no splicing wires.

if its a lot of highway miles, id say the cat is clean. but since all the
numbers are high, a new cat should clean it all up.

 

I actually had very similar results with my 1996 Acura Integra
recently (73k miles). I believe my cat is marginal as well. As you
can see, when it warms up, your numbers get better.

On the CO -- I'd probably look at the 02 before the cat. Acura has
an "special" extended emissions warranty on my year.. I don't know if
it covers cats though. Honda may have a similar program.

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N38.6 W121.4

 

I had my car in for a smog check a few weeks ago (Northern Cal). In
addition to the numbers you listed, I also got the O2 content of the
exhaust gases. There obviously is no test limit for O2 content, but if
you have the numbers, please post them. Those numbers are valuable for
diagnosing emissions problems.

 

Randolph asked:

O.k., didn't noticed those numbers before. But here they are:

RPM %CO2 %O2
Test Meas Meas Meas
M1: 15 mph 1927 15.2 0.0
M2: 25 mph 1989 15.1 0.0

Does this mean the O2 sensors are working properly?

 

Drive for two years and sell.

 

Whoa!

20 miles to warm up the car?

I'm warmed up, even in 30F ambient, by 1-2 miles at most. ('04 LX V6 coupe)

 

I think I, among others, recall correcting you on this before. No your
engine is not fully warmed up by 1-2 miles, not even in 80F weather. Just
because your coolant temp is in the normal range does not mean the engine
is up to full operating temp. In 30F it takes ~6-7miles for the oil to get
up to a stable temp.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

You may think so, but the cat is stone cold, relatively speaking. A cold
cat equals instant failure. You'd be high on all counts.

20 miles is great. 20 miles done properly is even better.

--
TeGGeR®

The Unofficial Honda FAQ
http://www3.telus.net/public/johnings/faq.html

How to find anything on the Internet or in Usenet Groups:
www.google.com
www.groups.google.com

 

It means there is no Oxygen left in the exhaust, a rich condition.
CO2 at 15.2 + CO at .5 = 15.7 which indicates approximately a 13.4 to
1 air-fuel ratio. The "ideal" air-fuel ratio is 14.7:1, anything
below it is rich, anything above 14.7 is lean.

I usually test Oxygen sensors w/ oscilloscopes.. I sometimes look at
rise/fall times. I usually look at frequency. I look at what happens
when enrich the mixture with propane (Does the O2 goto 800 mV?) and
with a vacuum leak (Does it goto 200 mV?) It's tough to do without
the proper equipment.

I worked on a 1987 car today that had the following readings:

CO2% 02% HC CO% NOx (ppm)

15 MPH 14.27 0.18 92 .82 813
25 MPH 12.50 0.12 174 3.64 579

The owner replaced the Oxygen sensor and the exhaust manifold which
had a hairline crack. I suspect he didn't need to do either. What I
found was that periodically, the mixture control solenoid would work,
sometimes it wouldn't. If I leaned the system out enough, the
computer would SOMETIMES pulse the solenoid (which I verified as being
good) and I would be in "fuel control" for a couple seconds. The O2
toggled normally. After investigating, I found that a coolant
temperature sensor wire was not securely crimped to its connector.
Wiggled the coolant temp sensor wire and amazingly, the mixture
solenoid would pulse normally. Ratioale: The car won't run in "fuel
control" if it's not hot enough. Since the wire was intermittent, it
would sometimes tell the computer it was warm enough to control fuel
and then tell it it was not. The coolant thermometer on the dash was
not the same signal as the one the computer was using to determine
closed loop mode.

After crimping the connector slightly, the car passed a the CA loaded
mode tests with flying colors.

But without scopes, dwell meter, and a fair amount of automotive
education -- I wouldn't have found it.

__________________
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N38.6 W121.4

 

Thank you all for the replies!

Tegger,

What is the proper way to warm up the catalytic converter?

 

(twiceasshort) spake unto the masses in

http://tinyurl.com/37xml

This is the ideal. Come as close to it as you can. You'd be amazed how far
the numbers can drop when proper pre-prep is followed.

http://tinyurl.com/yqh36


--
TeGGeR®

The Unofficial Honda FAQ
http://www3.telus.net/public/johnings/faq.html

How to find anything on the Internet or in Usenet Groups:
www.google.com
www.groups.google.com