braass91

Smog barely passed emissions but failed due to a vacuum line crack from visual inspection. The NO (PPM) and HC (PPM) barely passed at:

15 mph
NO (PPM) at 834 with max allowed of 835
HC (PPM) at 74 with max allowed of 91

25 mph
NO (PPM) at 605 with maximum allowed of 774

I have replaced the cracked vacuum line and want to do a re-test to pass. My question is, given the high readings above, is it better to do the re-test first thing in the morning or when the engine is hot, or does it matter? The first smog readings above was done first thing in the morning and the engine was still cold. Thanks

Former User

Theoretically it should not matter when the car is tested, as long as the engine is fully warmed up.

v4lu3s

i have always been told make sure the catalytic converter is as hot as possible since it is most efficient then. In other words drive it some before you test, get the coolant temperature up to the normal range and do not let it sit for a long time waiting to test.

ALLxMOTOR EG

This is kind of incorrect, a technician should not overcondition the catalytic converter to make it pass, if warmed up too much they shall let the car idle for 3 minutes. Therefore they can warm it up but shouldnt over warm up the CAT, i'm a smog tech btw.

To the OP, what is your CO reading?

4drEF

Considering you fixed a vacuum leak, it should pass easier now.

v4lu3s

I am not talking about overheating it etc, i am talking about making sure it is at full operating temp PRIOR to going to the smog test, and NOT letting it sit turned off in the parking lot for half an hour and cooling back down. I am pretty confident that you cannot guarantee that when someone arrives you can test them right away every time...and if the car is cold a 3 minute idle will NOT get it back to full operating temperature in many cases...

braass91

CO (%) readings are:

15 mph = .26 with max allowed of .57
25 mph = .11 with max allowed of .48

Thanks

v4lu3s

you are not running too rich that is for sure. your air fuel ration is right where it should.
is your ignition timing dead on? when were your plugs last replaced?
chances are if the vacuum line was causing a leak you SHOULD be doing better now.

ALLxMOTOR EG

Ok, you're right. Reading owns me lol.

But yes, OP it looks like you were running lean at first and you should be good to go for a re-test. If all fail replace the CAT and all HC, CO , and Nox will lower.

hatchmasterjay

true that. make sure you have a full tank of gas as well
your fuel will be cooler ..... this will make a difference too.

4drEF

That is the first time I have ever heard that.
Ever.
Full tank of gas makes fuel cooler?

hatchmasterjay

yes the more fuel in the tank = cooler gas. there is more of it there and less likely to heat up from exhaust temps.
an old smog tech told me taught me that trick
you could go a step further and run your fuel line along the suction line of your ac and actually cool your gas that way (porsche and benzo have been doing this for years)
cooler combustion chambers=lower nox numbers
on a car running rich they usually fail for high hc and co
but they will pass nox with flying colors.
correct the running rich issue and the nox numbers will come up significantly.
btw my car passed with flying colors today
and i am not a smog tech. lol

also the fuel pump is in the tank, the fuel is what actually cools it and keeps it from burning up.