Darn! My '94 Del Sol failed the California Smog Check today

After having passed the California smog check for 2 tests (4 years) in a
row, my stock '94 Del Sol ("S" model with 1.5L engine) failed today. :-(
It's the first time I've ever had any car fail the Smog Check, in 20 years
of living in California.

I have never made any modifications to the engine, and I take it in for
regular maintenance according to the maintenance schedule. It has been
about 6500 miles since its last oil change, and I don't use any pour-in fuel
additives. It is running normally with no noticeable engine problems.

Here in California the DMV has recently made the Smog Check test more
sophisticated, using a 'dynamometer' (treadmill) to test the car under load.
They test the car at a simulated 15mph and at 25mph. They also added a NOX
(nitrous oxide) emissions check, and that's the one that my car failed, but
only at 15mph.

As for my other emissions test results, my Del Sol had extremely low CO2,
O2, HC and CO emissions at both 15mph and 25mph, but failed the Nitrous
Oxide (NOX) test at 15mph. In fact, the NOX emission was about 3 times
higher at 15mph than at 25mph, which seems counter-intuitive. I had driven
the car at least 15 miles before arriving at the test facility, so it was
well warmed-up.

Has anyone else seen this kind of failure with an older Honda Civic or Del
Sol? If so, what was the culprit? I'm trying to get an idea how much it's
going to cost to have it fixed.

Thanks for any ideas, feedback, or sympathy.

-DK

 

NOX is usually a function of the EGR valve, which your car might not
have. timing can also effect it, so id check that and replace the
plugs/plug wires/dist cap/rotor with OEM if necessary.

went through all that with a 1975 MG midget. by the time i got the EGR
unclogged, the smog pump working right, and a new $99 catalytic
converter on, it passed with flying colors. IIRC, some of the emissions
were *0*.

the O2 sensor is likely long overdue, if its never been replaced. a
place that ISNT "test only" should be able to pinpoint the exact problem.

 

Post ALL your numbers, including the limits for your area.

Post ALL your numbers, including the limits for your area.

Post ALL your numbers, including the limits for your area.

If you were extremely low in HC and CO, that suggests either you're running
hot, timing is too far advanced, or your EGR system is not working
correctly.

You cannot be extremely low in CO2 if you were extremely low in HC and CO.
If you were very low in HC and CO, that means the cat has managed to bind
its stored oxygen to the CO and HCs to make them into CO2 and water. So CO2
ought to be HIGH.

 

AND your NOx numbers are high, I meant to say...

 

Hello and thanks for all the responses. Here are all of the Emmission Test
Result numbers from my failing test report:

= = = = = = = = = = = = = = =

Line 1:

Test=15mph
RPM=1727
%CO2 meas=15.6
%02 meas=0.0
HC (PPM) MAX=92, AVE=21, MEAS=13
CO (%) MAX=0.55, AVE=0.06, MEAS=0.03
NO (PPM) MAX=716, AVE=150, MEAS=991
FAIL
= = = = = = = = = = = = = = =

Line 2:

RPM=1904
%CO2 meas=15.5
%02 meas=0.0
HC (PPM) MAX=57, AVE=13, MEAS=11
CO (%) MAX=0.54, AVE=0.05, MEAS=0.02
NO (PPM) MAX=764, AVE=136, MEAS=354
PASS
= = = = = = = = = = = = = = =

-DK

 

For the Line 2 numbers, I forgot to type "Test = 25mph".

-DK

 

Good number there. Means the catalytic converter is successfully converting
the CO into CO2.

Good. Means the cat is soaking up oxygen properly, so it's in good shape.
It also suggests you don't have an exhaust leak.

Low number there. You're probably running lean.

You're running a bit lean.

California checks your ignition timing as part of the test, doesn't it?
Then we can rule that out.

Possible causes:
EGR passage to the EGR valve carboned up
Fuel pressure regulator weak
Rich-biased oxygen sensor

I'd run a bottle or two of Techron through it for the next week or so (just
to make sure the injectors and valve tops are reasonably clean) and then
take it back for a retest. If it still fails on the same thing, clean the
EGR passages.

 

<SNIP>

Just for kicks, change the PCV (since they never get changed) along with
using the injector cleaner. Anybody else think that will help? If the
PCV is wacky, doesn't the computer 'misread' some of it's variables?

'Curly'

 

variables?

From my reading and experience, yes, typically causing an
overly rich fuel mixture and so causing fuel mileage to
decline. But as I think we've discussed in the past, it's
the CO reading that should be out of spec for a bad PCV
valve.

A malfunctioning EGR system, among other things, is said to
be a possible cause of the high NOX. See
http://www.aircare.ca/index.php?repinfo-glossary.php ,
especially the "Causes of Excess Emissions" part. See also
http://www.interro.com/techgas.html#anchoreleven

But I agree that, if this is the original PCV valve, it's
due for replacement, if only for the sake of maximizing fuel
mileage and minimizing the chance of oil leaks.

 

theyre *supposed* to. whether the mechanic can read the marks correctly
is another story. and if it was done at a "test only" station, they
arent allowed to fix it, and arent even supposed to suggest a cause.

on my MG, the actual EGR valve was faulty. i applied vacuum to it with a
mityvac hand pump, or TRIED to. wouldnt work. took it off and inspected,
the diaphragm was split.

id vote for the timing being off.

 

Does a del sol have an EGR? My 98 civic 1.6 SOHC Non Vtec does not.

 

Status Update on my '94 Del Sol emissions:

The '94 Del Sol doesn't have an EGR.

Here are the results from the Visual Inspection/Functional Check Results
section of the Smog Check:

= = = = = = = = = =
EGR (visual)...N/A
PCV...Pass
Catalytic Converter...Pass
Fuel Cap Integrity...Pass
EGR(functional)...N/A
Thermostatic Air Cleaner...N/A
Air Injection...N/A
Ignition Timing: 9 BTDC...Pass
Spark Controls...Pass
Fuel Evaporative Controls...Pass
System Malfunction Light...Pass
Oxygen Sensor...Pass
= = = = = = = = = =

So I took the car to a "certified smog check and repair" station, and they
told me the following (the tests cost me $125):

500ppm, CO2 is borderline"

They told me I need a new catalytic converter, $299 installed (a 3rd party
repair shop does the work offsite). I decided to hold off for a few days
while I figure out what's going on.
= = = = = = = = = =

Thinking I might try to replace the CAT myself (I work on cars about once
every decade!), I called the local Kragen and they said they have a Maremont
"direct fit" replacement that costs $135. Here's a picture of it:
http://ecat.arvinmeritor.com/smartlink/exhaustspec.aspx?partnum=29132 I
didn't buy it, but I crawled under the car and removed the heat shields
surrounding the CAT to see if I'd have a chance at doing the job myself. I
can easily get at 4 out of 5 bolts that hold the CAT to the tailpipe
sections, but there's one bolt that is nearly impossible to loosen because
it's on the exact top of the tailpipe where there's very little room to
swing a rachet wrench. So I buttoned it back up and decided I'll have a
shop do the work. Do you know if a 'pro' would remove the entire exhaust in
order to swap out the CAT? I definitely don't want to get into that, with
all the rusted bolts and difficulty I'd have at getting at them.

A little history about my car: I looked back at its Smog Check results from
2004, and I noticed that it JUST BARELY passed the NOX spec at 15mph (it
scored 712ppm, and the MAX was 716ppm); all other numbers were well below
the MAX. So I guess this problem has been looming for a few years and it's
about time I 'clean up' the car's exhaust.

Thanks again for all your great input and ideas...this is a great forum for
learning.

David K.

 

Has it been 6,500 miles on the oil? My brother has a close friend who
works emissions tests in PA....says oil can affect the readings. Why not
try some high milage oil and see what happens? Good luck.

 

thats what i was wondering too. i dont think they do, which would mean
some kind of timing problem, at low speed. too retarded? advanced? is
there a vacuum thingie on the distributor?

 

a brand spanking new cat would likely do it, as well as dropping the
other applicable numbers even lower.

 

Just a follow-up for anyone who's following this thread:

The Del Sol has passed the emissions retest. (Yes, you just heard a
champagne cork popping.)

It cost me $299 to get the Catalytic Converter replaced, which I thought was
a decent price (the part alone would have cost me $135 at Kragen Auto
Parts). It now passes all emissions tests with flying colors; the 15mph NOX
reading dropped to less than 1/3 of what it was before. I had the oil
changed too, since I was overdue on that.

All in all, I spent about $540 on this Smog Check adventure, for the smog
test, problem diagnosis, CAT replacement, and smog retest. :-( But I guess
it's worth the price so my neighbors can breathe easier.

Thanks again to all of you for your advice, hypotheses, and words of wisdom!

David K.

 

if its got the original O2 sensor, it might be worth replacing. id
definately do it if you notice any degredation in the next test, in 2
years.

my 2005 test was cleaner than my 2003 test, and the only difference was
a fresh O2 sensor.