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Old 4th March 2007, 02:53   #1
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Default O2 / Lamda sensor? What do they do ?

hey
what are o2 sensors ? what do they do ?
please redirect me to another froum if this is already answered
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Old 4th March 2007, 10:41   #2
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oxygen sensors , detect the amount of oxygen in the exhaust, this information they pass on to the Engine Control Unit, which deduces if the air:fuel mixture is running rich or lean.

Rich mixture meaning more fuel : less oxygen in the exhaust
Lean Mixture meaning less fuel : more oxygen in the exhaust

the engine control unit then varies the fuel injection time to make the mixture perfect i.e neither rich nor lean
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Old 4th March 2007, 14:35   #3
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Recently there has been a contaminated fuel problem in UK. Several thousand cars O2 sensors had to be replaced.

See here
BBC NEWS | UK | Fuel depot probes 'contamination'

When sensors determined that the oxygen content in exhaust is not within limit, it signals the same to ECU, which then converts the engine into "limp home" mode (usually restricting rev to 2000 RPM). Thus cars can only crawl to a garage!

Many people reported that their cars shuddered, lost power etc.
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Old 5th March 2007, 21:06   #4
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Well i just had these o2 sensors on my bimmer changed. The car was missing and running as if straned. HAve to yet pick it up from navnit and see whether the job is done.
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Old 5th March 2007, 22:24   #5
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An O2 sensor in a car is an active part of its pollution control mechanism. Its main job is to detect if the mixture coming into the exhaust is lean or rich. Its appropriately signals the ECU to compensate by adjusting the amount of fuel in the next combustion cycle.
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Old 5th March 2007, 23:49   #6
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an o2 sensor is an integral part of modern mpfi systems where it determines the amount of o2 in the exhaust gases and based on these values the ecu calculates the air fuel ratio of the intake mixture.
if there is too much o2 in the exhaust it means the mixture is lean, thus the ecu increases the injector pulse width to supply more fuel
this sensor helps in better mileage and power as the right amount of fuel is being supplied at all loading conditions
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Old 6th March 2007, 01:31   #7
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What you have in your stock car is a narrow band sensor, it will simply indicate to the ECU if it is ideal 14.7 or not.

Some cars come with stock heated O2 sensors so that during cold starts the ECU gets to correct the AFR without having to wait for the exhaust gasses to warm up the sensor.

Some cars have 2 sets of O2 sensors to determine if your Catalytic con is working correctly, it compares the o2 content before and after the cat, these are basically indicated as bank1 and bank2 on many OBD2 software even if you have a inline 4 or inline 6...

For tuning/modding purpose wideband O2 sensors are used.. they indicate if you are running rich and by how much, a narrow band will simply indicate you are off the mark but tell "by how much" .. eg at WOT for getting power someone may use AFR of 16..if it was a narrow band we wouldn't know this..

Basically the sensor either narrow band or wideband , heated or non heated .. indicates the AFR by means of a voltage signal to the ECU.
this voltage signal fluctuates depending on the difference in O2 content in the exhaust manifold with respect to the atmospheric 02 content.
the o2 sensor basically has a coating which is exposed to both the exhaust gas and the atmosphere. This coating generates a specific amount of reference voltage at a particular temperature, so the sensor needs to be at a correct operating temperature before it can work correctly.
Thats why the ECU remains in open loop till the sensor comes to correct temperature and does not bother about voltage signal from the o2 sensor, this explains your engine idling at hi RPM in the morning..

The coating on the sensor is very sensitive to contaminants in the fuel so they get damanged when you use bad fuel..

Dude ..there is more to this..above is just a quick basic info for o2 sensors and what they do and how they work etc

Last edited by chetanhanda : 6th March 2007 at 01:35.
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Old 6th March 2007, 05:44   #8
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Nice explaination Chetan...

Quote:
Originally Posted by chetanhanda
a narrow band will simply indicate you are off the mark but tell "by how much"
Though I think the word "not" is missing in this sentence?


Also, check out the link in this (Oxygen Sensor - Malfunction Need Help) post.

cya
R
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Old 6th March 2007, 11:54   #9
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Quote:
Originally Posted by Rehaan View Post
Nice explaination Chetan...
Though I think the word "not" is missing in this sentence?
Also, check out the link in this (Oxygen Sensor - Malfunction Need Help) post.
cya
R
yes ...exactly what I was saying..
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Old 8th March 2007, 01:32   #10
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thanks a lot people cleared a lot of things in my heaD
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Old 8th March 2007, 11:19   #11
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Perhaps you could go through this thread for more info on working of O2 Sensor
http://www.team-bhp.com/forum/techni...-yourself.html (Weird "Engine Management" probs & TIP on how to check Honda engine codes yourself !!)
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