The various chemicals emitted in exhaust gasses from an internal combustion engine. The usual gasses which are measured through emissions testing are Nitrogen Oxide (NO2), Carbon Monoxide (CO2), and HydroCarbons (HC).
Questions tagged [emissions]
155 questions
38
votes
3 answers
What does a water-like drip coming out of the exhaust of the car signify?
Sometimes while driving in the traffic, I come across a car or two which would be dripping water-like drops from its exhaust steadily in 4-5 second intervals. I tried to ask a couple of people at the local workshops; they say, and I quote, "The car…
Sandman
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What is the point of the exhaust?
I was thinking today, what is the actual point of an exhaust?
Why can't we just have a pipe going out the front of a car instead of taking all the gases to the back of the car?
I can only see disadvantages of the current design:
The expense of…
George
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11
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3 answers
What could cause high HC and CO, but low NO and CO2 in a smog test
Despite my confidence in having a (relatively) new catalytic converter and a new O2 sensor, my lovely 1994 BMW 325i Convertible got flagged as a "Gross Polluter." The test results are summarized below:
CO2 O2 HC CO NO
13.6 0.1 333 …
Hari
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11
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2 answers
How does raw fuel damage the catalytic converter?
I was wondering, if fuel gets in the catalytic converter, how does it damage it?
George
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11
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2 answers
How are diesel engines better for the environment than gasoline?
I understand that diesel engines have become much more efficient at controlling emissions over the last couple decades. Various websites like this one describe the technological improvements that have brought this about, such as:
Direct injection…
Poisson Fish
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11
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3 answers
Why don't all diesel engines have throttle plates?
I learned recently that many older and some newer diesels don't have throttle plates to control airflow. I was also quite shocked to learn about a condition called diesel engine runaway. Apparently a diesel engine can run out of control from oil…
DucatiKiller
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8
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1 answer
What is the "Activated Carbon Cannister"?
Why do I have an "Activated Carbon Cannister" in my unleaded/petrol car?
What is it's purpose?
How does it work?
Do I need to do anything to maintain it?
I would like a general answer, but my car is a 2003 Opel Agila if you want to be specific!
George
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8
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Connecting to the Battery During Emissions Testing to Measure RPMs?
When doing emissions testing, they connect to the battery, either directly, or using the cigarette lighter socket.
I'm assuming that this is to measure the RPMs, as the only other thing connected to the car is a gas analyzer in the tail pipe.
I'm…
Robert S. Barnes
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7
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2 answers
Should I replace my own oxygen sensor if i have a Check Engine Light and Code P2195?
My 2003 focus lx 2.0L L4 SOHC ~18,000 miles has had the engine light so i went to autozone to read the code.
Autozone obd2 printout says "P2195 lack of heated oxygen sensor- Bank 1 Sensor 1 HO2S11 switch- sensor indicates lean."
Autozone said "Your…
catjacent
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Emissions - High CO reading only
My 1999 Honda CRV has just failed it's UK MOT test on emissions.
Results are below:
1st test:
CO 0.73 (FAIL - max is 0.30)
HC 78 (PASS - max is 200)
Lambda 1.008 (PASS - between 0.970 & 1.030)
2nd test:
CO 0.59 (FAIL - max is 0.30)
HC 76…
GoldieLocks
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4 answers
What effect will removing my EGR have?
My 2003 Jetta TDI check engine light recently came on, and a scan by Advance Auto revealed code P0401 -- EGR insufficient flow.
I took the vehicle to the local TDI guru, who gave me the option of removing the EGR from the system entirely, and…
Flimzy
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7
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3 answers
Why are VW recalling their cars to remove a defeat device?
As I understand it, Volkswagen had software to artificially enhance their efficiency ratings on a test rig. Since it would only be active under test, what is the point of recalling millions of cars to remove software that will never be run?
I can…
Jon Bates
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How to know whether a Lexus rx450h qualifies for California Emissions standards?
I'm looking at a 2012 Lexus rx450h but will be moving to one of the states (Arizona, Connecticut, Maine, Maryland, Massachusetts, New Jersey, New Mexico, New York, Oregon, Pennsylvania, Rhode Island, Vermont, and Washington, as well as the District…
WilliamKF
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4 answers
Emissions Problem: Lambda AND CO Slightly High on my 98 Mazda 626
I just took my 98 Mazda 626 for it's inspection and they said the carbon monoxide is slightly high. The test is done using a tail pipe gas analyzer while holding the RPMs between 2500 - 2800 for thirty seconds.
From what I've read, this is normally…
Robert S. Barnes
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6
votes
4 answers
Cheap vs Expensive Fuels
What is the difference between the cheapest fuels in a place like Tesco's and the 'high quality', highly priced competitors? Is there actually any noticeable difference in available power, engine smoothness, efficiency, maintenance costs…
Max Goodridge
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