Smog Test cheats, How do they do it?

[zmelli]

I am looking for a used car and have stumbled accross cars that have questionable Smog Test Results:

15 MPH HC (PPM) Max 61 PPM; Measured 61 PPM. AVE 4 PPM

25 MPH HC (PPM) Max 45 PPM; Measured 45 PPM. AVE 4 PPM

How does the Test Station cheat the machine? Mostly dealers are doing this.

 

[bdcardinal]

They stick the probe in the tailpipe of a different car and match the RPM to the car being tested.

 

[HTSS_TR]

As bdcardinal said, normal cheating is hook up the test probe in another car and enter the VIN of the test car into computer. But the test results that matches exactly the max allowed is something else. How they alter the numbers to just pass the test on the computer is unknown to me.

 

[stephen9666]

Someone I know had a ghetto shop cheat on the test several years ago. They said the shop unplugged the fans on his car so it got hotter than normal. That cleaned up the exhaust enough so it passed.

Why that would have worked, I don't know.

 

[fdcg27]

I'm sure that for a Hamilton, the test station can figure out how to get the numbers needed for the car to pass.
This happened in Ohio when we still had widespread testing, and probably happens today in those counties where testing is still required.
For every test station employee caught, how many got by with it?

 

[demarpaint]

Originally Posted By: bdcardinal
They stick the probe in the tailpipe of a different car and match the RPM to the car being tested.


+1 or they'll put a big fan in front of the grill and force a large volume of air through the grill. One of the more common ways using another car and disabling the camera if one exists.

 

[The_Jeff]

Can you get previous years' results from the state? IIRC you can online. I wonder if you are getting some weird automatic exemption like the car was brought in from out of state and they paid the "impact fee".

 

[yonyon]

It could also be that those readings are for real, but actually worse than they would be if the test were done correctly. If the engine and/or cat(s) aren't up to full operating temperature the emissions may be high. The pollutant levels drop with the temperature increase during the test until they reach the pass fail mark, then the emissions analyzer goes "DING! PASS" or the equivalent. I'm not familiar with how things are done in Cali, but it happens here in NJ all the time.

 

[bluestream]

Originally Posted By: stephen9666
Someone I know had a ghetto shop cheat on the test several years ago. They said the shop unplugged the fans on his car so it got hotter than normal. That cleaned up the exhaust enough so it passed.

Why that would have worked, I don't know.

 

[Chris142]

It's called clean piping. I dunno how they get past. The cel though

 

[yonyon]

Chris142, not all cars have a CEL that's an issue. Older cars don't even have a CEL and there are many, especially Hyundai and Euro import, that don't turn on the CEL when they really should. Custom PCM programming can also get past the CEL issue. I know of one person in my area that had a PCM replaced and flashed with Mexico Emissions programming by the local Dodge dealer. This thing dumps so much raw fuel it makes my eyes water and it's barely drivable because with and moderate to high acceleration the turbo blowoff valve gyrates so fast between open and closed.... I'm getting sick thinking about this car. Anyway, it passes the OBD test at the state lanes every time.

 

[The_Jeff]

It could also be that those readings are for real, but actually worse than they would be if the test were done correctly. If the engine and/or cat(s) aren't up to full operating temperature the emissions may be high. The pollutant levels drop with the temperature increase during the test until they reach the pass fail mark, then the emissions analyzer goes "DING! PASS" or the equivalent. I'm not familiar with how things are done in Cali, but it happens here in NJ all the time. [/quote

This is the most plausible explanation yet.

I know Mass inspection lane computers take a photo of the front of your car (usually including license plate) and transmits it to the RMV computers.

 

[dparm]

In Illinois it's quite difficult -- OBD2 cars don't take the sniffer unless there's a CEL. They plug in the connector, check for readiness, look for codes, and then you drive out. Takes all of 3 minutes. And yes, there is a camera on every bay.

 

[Barkleymut]

Wow I'm glad that we don't have emissions testing here, I would say something really political but that wouldn't accomplish anything and i would get banned

I don't understand if a car is dumping fuel how it could possibly pass an emissions test, oh thats right politicians came up with it...gotta stop now

 

[The_Jeff]

The typical emissions testing scenario is the feds get on a state's case because a municipal unit (usually a county) had too many "bad air days" over a set time period. The county needs to come up with a plan to fix it. Sometimes they choose emission testing, sometimes doctored gas, sometimes something not even car related.

They have to pay consultants all sorts of money to prove it should work. Once passed, it stays on the books, unless they pay the consultants even more money to say it's not needed anymore.

My county needs an OBDII scan and gas cap pressure test. The gas cap is redundant (usually) as the car would throw an EVAP code... but it's how the law is written.

The Northeast may or may not be naturally cleaner... we get acid rain from the rest of the country especially coal burners. But my state is too broke to see if they could get away with dropping the requirement. And surely the dealer/repair lobby would not want to lose that.

 

[zmelli]

Originally Posted By: eljefino
Can you get previous years' results from the state? IIRC you can online. I wonder if you are getting some weird automatic exemption like the car was brought in from out of state and they paid the "impact fee".


http://www.bar.ca.gov/pubwebquery/vehicle/pubtstqry.aspx

maybe your state has a site like this

 

[zmelli]

As a Electronic Tech I was thinking maybe a probe simulator is being used. A millivolt source or decade box in place of the probe.

 

[Vikas]

But if they are cheating, why stop at the limit? They will pick the number to be average rather than at the end of the scale. I do not think there is any cheating. The vehicle just happens to have borderline emission.

 

[Loobed]

In California, the newer American cars (2000+) get put on a dyno, and they read the info off the OBD-2 computer. Nothing gets stuck in the tailpipe.

 

[zmelli]

Originally Posted By: Loobed


In California, the newer American cars (2000+) get put on a dyno, and they read the info off the OBD-2 computer. Nothing gets stuck in the tailpipe.


I think it depends on the county you live in. Tail pipe is probed in Southern California.