# How long to warm up the car before smog test?



## alee (Dec 19, 2001)

Getting my car smog tested in CA for the first time.

2001 330Ci, 36.7k miles, Shark injector, otherwise stock... pretty sure I'll pass, but wasn't sure what the general consensus was about how long I should warm up the car before heading into the test station.

-Al


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## ganesht (Sep 9, 2008)

go drive on the highway for 20 mins.. you need to make sure the cats are nice and hot..


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## Bruce (Dec 24, 2001)

OBDII cars are sniff tested....they query the computer for fault codes. No need to have the car warm.


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## jcatral14 (Aug 4, 2003)

What I want to know is how you have an '01 car and only have 37k miles on it  Go out and drive 

Sorry no constructive input. The other suggestions seem plausible.


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## ganesht (Sep 9, 2008)

Bruce said:


> OBDII cars are sniff tested....they query the computer for fault codes. No need to have the car warm.


how do you figure that?

the sniffer tests the exhaust checks co2/no output as well as unburnt hydrocarbons...
the cats (when at operating temp 400-600deg c) do the following chemical conversions:

Reduction of nitrogen oxides to nitrogen and oxygen: 2NOx -> xO2 + N2
Oxidation of unburnt hydrocarbons to carbon dioxide and water: CxH2x+2 + 2xO2 -> xCO2 + 2xH2O
Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 -> 2CO2

how do they do this? by using platinum, rhodium, palladium, cerium, iron, manganese, and nickel as catalysts along with intense heat.

so my point of running the car was not to get the engine temp up, but rather the cats to operating temp...

if you believe theres no need to have the car warm, next time you need to get the smog checked on one of your cars how about you leave the car there over night and test it first thing in the morning while the cats are cold.. it doesn't matter how new your car is i bet you it will fail.


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## ganesht (Sep 9, 2008)

Bruce said:


> OBDII cars are sniff tested....they query the computer for fault codes. No need to have the car warm.


i understand that Smith County is one of the countys in texas which require an annual smog test, but ca has the nations toughest emission regulations.


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## alee (Dec 19, 2001)

jcatral14 said:


> What I want to know is how you have an '01 car and only have 37k miles on it  Go out and drive .


Last year I drove 500 miles. :eeps: That's NYC living for you... keep a car, thinking you'll take it out every weekend to get out of the city and end up never leaving the city.


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## Bruce (Dec 24, 2001)

ganesht said:


> i understand that Smith County is one of the countys in texas which require an annual smog test, but ca has the nations toughest emission regulations.


Smith County does NOT have smog tests. I have lived in the DFW area (that does require smog tests just like CA has) with pre-OBDII cars and OBDII cars....the pre OBDII cars got put on the rollers and a probe stuck up the tailpipe to test emissions. The OBDII cars go pulled into an empty bay and hooked up to the computer the check fault codes. The theory is if there are no faults codes the system is operational and the car is not putting out excess emissions.

Or are you saying that CA now requires the OBDII computer query AND a sniff test?


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## ganesht (Sep 9, 2008)

Bruce said:


> Smith County does NOT have smog tests. I have lived in the DFW area (that does require smog tests just like CA has) with pre-OBDII cars and OBDII cars....the pre OBDII cars got put on the rollers and a probe stuck up the tailpipe to test emissions. The OBDII cars go pulled into an empty bay and hooked up to the computer the check fault codes. The theory is if there are no faults codes the system is operational and the car is not putting out excess emissions.
> 
> Or are you saying that CA now requires the OBDII computer query AND a sniff test?


Really i thought smith county was one of the tested counties.. my bad
just wondering but when was the last time you needed to get any of your cars smogged?

yep ca requires odb2 cars to pass the sniffer..

pre odb require the sniffer under load, or tsi to be done..

none the less, all smog test in the state of ca and ct require you to get the sniffer, thus you need to have your cats all nice and hot..


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## Fast Bob (Jun 4, 2004)

"Best-case scenario" is to pull into the inspection station immediately after highway cruising for 20 or more minutes....


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## alee (Dec 19, 2001)

Passed smog this morning, but am a little concerned by the numbers...










The NO numbers seem much higher than they probably should be. Thoughts?


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## ProjectZHP (Apr 22, 2009)

sparkplugs and some Techron fuel injection cleaner might help your NO levels. Seriously. They're not up by much and this is common with Higher output turbo charged auto's


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## jesimmons (Jan 11, 2008)

ganesht said:


> how do you figure that?
> 
> the sniffer tests the exhaust checks co2/no output as well as unburnt hydrocarbons...
> the cats (when at operating temp 400-600deg c) do the following chemical conversions:


I don't know the test procedure in CA. In VA they *USED* to insert a probe into the tailpipe and measure CO and NO2. With the advent of OBDII systems that monitor emissions systems, VA has changed their certification procedure to only hook up to OBDII and check for the fault codes indicating an emissions system problem. If there are no fault codes, you pass.

I think what was meant above is that they "sniff" the OBDII system for fault codes... not sniff the tailpipe for NO2 and CO.


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## Grentz (May 16, 2009)

jcatral14 said:


> What I want to know is how you have an '01 car and only have 37k miles on it  Go out and drive
> 
> Sorry no constructive input. The other suggestions seem plausible.


My 03 has 5000 miles on it


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## alee (Dec 19, 2001)

jesimmons said:


> I think what was meant above is that they "sniff" the OBDII system for fault codes... not sniff the tailpipe for NO2 and CO.


They definitely put something into the tailpipe to physically sniff for NOx and CO.


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## ganesht (Sep 9, 2008)

alee said:


> They definitely put something into the tailpipe to physically sniff for NOx and CO.


yep ca checks for obd codes as well as using the tailpipe sniffer to check levels...


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## anE934fun (May 10, 2008)

ganesht said:


> yep ca checks for obd codes as well as using the tailpipe sniffer to check levels...


And, in certain areas (S.F. Bay Area and SoCal for example), the car is put on rollers and tested 'on-the-road' (the rollers act as a pseudo 'road test'). As alee's report shows, there are two tests that are done. Fail either test, and your car is in deep trouble. The NOX measurement result is low, even though it appears high.


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## jesimmons (Jan 11, 2008)

ganesht said:


> yep ca checks for obd codes as well as using the tailpipe sniffer to check levels...


Ahhh... Back when VA did the tailpipe snifaroo, I would drive the car till the engine was at full operating temp before taking it to get inspected. The inspector as I recall took readings at certain RPM levels with the car in gear (the drive wheels of course were on some roller device to measure simulated driving speed).


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