Omega Owners Forum
Chat Area => General Discussion Area => Topic started by: VX1 on 07 March 2008, 20:43:31
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Does anyone know how a Lambda probe and Cat works? And when they should be replaced (Lambda probe) and what to look out for to know when the cat(s) are going?
Paul :y
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Does anyone know how a Lambda probe and Cat works? And when they should be replaced (Lambda probe) and what to look out for to know when the cat(s) are going?
Paul :y
cats filter all the harmfull gasses in exhaust fumes and the lamdas check the mixture to keep it running sweet !! when your cats are gone they will rattle break up and block up your exhaust !! perfeormance will drop also !! :y
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Does anyone know how a Lambda probe and Cat works? And when they should be replaced (Lambda probe) and what to look out for to know when the cat(s) are going?
Paul :y
cats filter all the harmfull gasses in exhaust fumes and the lamdas check the mixture to keep it running sweet !! when your cats are gone they will rattle break up and block up your exhaust !! perfeormance will drop also !! :y
Correct thats the basic workings of it, BUT do you know WHY the cats break up and how?
Paul :y
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Does anyone know how a Lambda probe and Cat works? And when they should be replaced (Lambda probe) and what to look out for to know when the cat(s) are going?
Paul :y
cats filter all the harmfull gasses in exhaust fumes and the lamdas check the mixture to keep it running sweet !! when your cats are gone they will rattle break up and block up your exhaust !! perfeormance will drop also !! :y
Correct thats the basic workings of it, BUT do you know WHY the cats break up and how?
Paul :y
tends to be from contamination from oil wrong type of fuel unburnt fuel from jump starting towing off large impact can break them up !! :y
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You been looking this up markey mark? Yet again Correct. :y
What about the lambda's then how do they work and when should they bee changed?
Paul :y
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Could this cause missfiring? on a 4 pot. :)
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Could this cause missfiring? on a 4 pot. :)
Yes. But also check your ignition system as well. Check the leads, and check if there is any oil in the plug wells as well.
Paul :y
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Could this cause missfiring? on a 4 pot. :)
Yes. But also check your ignition system as well. Check the leads, and check if there is any oil in the plug wells as well.
Paul :y
Yes, done that, new gasket, plugs and leads. Have a new dis thing to fit when itgets warmer, just exhaust makes a funny rattle and wondered if there might be a connection. No eml light, new cam and crank sensor. :)
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You been looking this up markey mark? Yet again Correct. :y
What about the lambda's then how do they work and when should they bee changed?
Paul :y
no paul im a car mechanic bud !! a good bit smarter than your average spanner man !!! :y
as for changing lambdas i wouldnt until they were faulty ! as long as you get them very hot they will last a very long time they tend to break after contamination :y
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You been looking this up markey mark? Yet again Correct. :y
What about the lambda's then how do they work and when should they bee changed?
Paul :y
no paul im a car mechanic bud !! a good bit smarter than your average spanner man !!! :y
as for changing lambdas i wouldnt until they were faulty ! as long as you get them very hot they will last a very long time they tend to break after contamination :y
Our servey say's..........X (family fortunes sound)
The lambda probes (sensor) should be checked for efficiency so that they are working correctly. Suggested check 30,000 miles approx. Replaced between 60,000 and 70,000 miles,(I will check this) as the sensor looses efficiency over time. This is due to wear and tear, nothing can prevent this of course. If the car has done 100,000 miles plus since the last change of the sensor it is recommended to replace as the emmisions will be through the roof not necesseraly the cat. The cat could be in perfect working order BUT the cat could play apart in this sudden increase in high exhaust emissions. I do believe this is right but clarification tomorrow will determin this.
Paul :y
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You been looking this up markey mark? Yet again Correct. :y
What about the lambda's then how do they work and when should they bee changed?
Paul :y
no paul im a car mechanic bud !! a good bit smarter than your average spanner man !!! :y
as for changing lambdas i wouldnt until they were faulty ! as long as you get them very hot they will last a very long time they tend to break after contamination :y
Our servey say's..........X (family fortunes sound)
The lambda probes (sensor) should be checked for efficiency so that they are working correctly. Suggested check 30,000 miles approx. Replaced between 60,000 and 70,000 miles,(I will check this) as the sensor looses efficiency over time. This is due to wear and tear, nothing can prevent this of course. If the car has done 100,000 miles plus since the last change of the sensor it is recommended to replace as the emmisions will be through the roof not necesseraly the cat. The cat could be in perfect working order BUT the cat could play apart in this sudden increase in high exhaust emissions. I do believe this is right but clarification tomorrow will determin this.
Paul :y
i would disagree paul only ever had to change one !! if a car passes its mot emmisions test then the lambda is doing its job ! im of the old school mate will not change things untill they go wrong except cam belts and tensioners !! :y
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You been looking this up markey mark? Yet again Correct. :y
What about the lambda's then how do they work and when should they bee changed?
Paul :y
no paul im a car mechanic bud !! a good bit smarter than your average spanner man !!! :y
as for changing lambdas i wouldnt until they were faulty ! as long as you get them very hot they will last a very long time they tend to break after contamination :y
Our servey say's..........X (family fortunes sound)
The lambda probes (sensor) should be checked for efficiency so that they are working correctly. Suggested check 30,000 miles approx. Replaced between 60,000 and 70,000 miles,(I will check this) as the sensor looses efficiency over time. This is due to wear and tear, nothing can prevent this of course. If the car has done 100,000 miles plus since the last change of the sensor it is recommended to replace as the emmisions will be through the roof not necesseraly the cat. The cat could be in perfect working order BUT the cat could play apart in this sudden increase in high exhaust emissions. I do believe this is right but clarification tomorrow will determin this.
Paul :y
i would disagree paul only ever had to change one !! if a car passes its mot emmisions test then the lambda is doing its job ! im of the old school mate will not change things untill they go wrong except cam belts and tensioners !! :y
Fair comment. I am with you on this one, if it don't need replacing don't replace it. Its just what I have been told when I went on the course through my company, the course was for "ENGINE MANAGEMENT AND DIESEL INJECTION" As I have been on the course I am now the 'EMS expert'. I sat there for the whole day and listened to people give presentations on the EM, Injector's, Lambda's, AFS etc to do with engine management. (terribly sorry old boy, I am a little tired)
As said though I am a bit old school as well. Top marks anyway MM you have completed your exam ;D ;D
Paul :y
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cheers paul ! quite a while since i had to use my brain like that ! been working as a mechanical fitter on steelworks for last 8 years !! just do cars at home on the side now !! :y
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cheers paul ! quite a while since i had to use my brain like that ! been working as a mechanical fitter on steelworks for last 8 years !! just do cars at home on the side now !! :y
Glad to be of some help to you then MM. Still got the brain power to answer some of the questions of your past life ;D ;D
Same here, but the annoying thing is, is when someone ask's you to do a job for them which should only take a weekend to do ends up taking 8 months because they cant be a55ed to get there a55 into gear and get the parts for you or drop the money of to you either, Like I have got, the guy that wants me to do his 2.2 omega (oil cooler) I have had his car here at home for the past 8 months not doing anything so still waiting for the money to get the parts. Once I have done the job for him he will need to pay me extra money for the storage of his car as well.
Paul :y
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cheers paul ! quite a while since i had to use my brain like that ! been working as a mechanical fitter on steelworks for last 8 years !! just do cars at home on the side now !! :y
Glad to be of some help to you then MM. Still got the brain power to answer some of the questions of your past life ;D ;D
yea i scare myself sometimes !! only hope it stays there for a good long time paul !! :y
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cheers paul ! quite a while since i had to use my brain like that ! been working as a mechanical fitter on steelworks for last 8 years !! just do cars at home on the side now !! :y
Glad to be of some help to you then MM. Still got the brain power to answer some of the questions of your past life ;D ;D
yea i scare myself sometimes !! only hope it stays there for a good long time paul !! :y
Sorry mate was just modifying the post. :y
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no worries fella ! know exactly what you mean though !!! drives me insane bud ! :y
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The modern lambda sensors can last the life of the car as can the cats and this is thanks to modern engiens and fuel injection setups.
Cats tend to be destroyed by contamination or over heating (miss fires result in unburnt fuel lighting on the precious metal noneycomb) but, the most common seems to be impact damage but, I guess thats thanks to all these bloody speed humps!
Ow yes, cats dont filter anything, they act as a catalyist to allow the various toxins and gases to chemicaly react and form less nasty gases etc.....hence why they are formed as a honeycomb in order to create the largest surface area possible for the gases to make contact with.
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The modern lambda sensors can last the life of the car as can the cats and this is thanks to modern engiens and fuel injection setups.
Cats tend to be destroyed by contamination or over heating (miss fires result in unburnt fuel lighting on the precious metal noneycomb) but, the most common seems to be impact damage but, I guess thats thanks to all these bloody speed humps!
Ow yes, cats dont filter anything, they act as a catalyist to allow the various toxins and gases to chemicaly react and form less nasty gases etc.....hence why they are formed as a honeycomb in order to create the largest surface area possible for the gases to make contact with.
what i said basically !! ::)
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.. and as for Lambda sensors, Wikipedia has a good article.
http://en.wikipedia.org/wiki/Lambda_sensor
Essentially the narrow band sensors used in most cars measure the balance of oxygen remaining in the exhaust gases. If the mixture going into the engine is rich (too much fuel) almost all the oxygen gets used up burning the fuel and you get very little left in the exhaust gas. A lean mixture results in almost all the fuel burning and some oxygen is left over, meaning a relatively high oxygen content in the exhaust.
The ideal fuel mixture, and the one where the balance of exhaust gases provide the right conditions for the catalytic converter to do its' job is somewhere between the two.
The voltage output of a narrow band lambda sensor underoes a rapid transition from about 0.2v to 0.8 v at this point, called the stoichiometric mixture.
During most running conditions (idling, cruising and gentle acceleration, with a hot engine) the engine management system runs in closed loop mode where it makes adjustments to the fuelling based on the lambda sensor output. The fuelling is constantly increased or decreased to keep the lambda sensor output "tipping" either side of stoichiometric. This is why people refer to Lambda sensors "switching". The constant corrections of the ECU cause the Lambda sensor output to cycle between 0.2 and 0.8 volts.
Put your foor flat on the floor and a stoichiometric mixture will give you poor performance and rather high combustion temperatures, possibly leading to knock, burnt out exhaust valves and melted pistons. For this reason, under heavy load the ECU will go open loop, ignore the Lambda sensor and use the inputs from the other sensors to determine from a map what fuelling to use to provide a considerably richer mixture. Stoichiometric mixture is a ratio of 14.7:1 air to fuel by mass. Under full load a normally aspirated engine will need to richen to probably around 12.8 - 13:1 for maximum power output. For a turbocharged or supercharged engine the mixture needs to be stinky rich - often 11 - 12:1). A narrowband Lambda sensor can't measure this rich so its' output is ignored in open loop mode.
A wideband Lambda sensor works over a much wider range of fuel mixtures and responds faster so an ECU can remain in closed loop operation over the whole range of engine operation. They are not widely used, but when they are, it's usually on turbocharged or supercharged engines where it's important to control the fuel mixture at a rich level under boost to protect the engine. They are also rather useful for mapping engines because they tell you exactly what's going on fuel-wise.
When a sensor dies it generally stops responding to the mixture or responds too slowly. The ECU will detect these conditions and light the EML so you don't need to change the sensors as a matter of course.
Kevin
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.. and as for Lambda sensors, Wikipedia has a good article.
http://en.wikipedia.org/wiki/Lambda_sensor
Essentially the narrow band sensors used in most cars measure the balance of oxygen remaining in the exhaust gases. If the mixture going into the engine is rich (too much fuel) almost all the oxygen gets used up burning the fuel and you get very little left in the exhaust gas. A lean mixture results in almost all the fuel burning and some oxygen is left over, meaning a relatively high oxygen content in the exhaust.
The ideal fuel mixture, and the one where the balance of exhaust gases provide the right conditions for the catalytic converter to do its' job is somewhere between the two.
The voltage output of a narrow band lambda sensor underoes a rapid transition from about 0.2v to 0.8 v at this point, called the stoichiometric mixture.
During most running conditions (idling, cruising and gentle acceleration, with a hot engine) the engine management system runs in closed loop mode where it makes adjustments to the fuelling based on the lambda sensor output. The fuelling is constantly increased or decreased to keep the lambda sensor output "tipping" either side of stoichiometric. This is why people refer to Lambda sensors "switching". The constant corrections of the ECU cause the Lambda sensor output to cycle between 0.2 and 0.8 volts.
Put your foor flat on the floor and a stoichiometric mixture will give you poor performance and rather high combustion temperatures, possibly leading to knock, burnt out exhaust valves and melted pistons. For this reason, under heavy load the ECU will go open loop, ignore the Lambda sensor and use the inputs from the other sensors to determine from a map what fuelling to use to provide a considerably richer mixture. Stoichiometric mixture is a ratio of 14.7:1 air to fuel by mass. Under full load a normally aspirated engine will need to richen to probably around 12.8 - 13:1 for maximum power output. For a turbocharged or supercharged engine the mixture needs to be stinky rich - often 11 - 12:1). A narrowband Lambda sensor can't measure this rich so its' output is ignored in open loop mode.
A wideband Lambda sensor works over a much wider range of fuel mixtures and responds faster so an ECU can remain in closed loop operation over the whole range of engine operation. They are not widely used, but when they are, it's usually on turbocharged or supercharged engines where it's important to control the fuel mixture at a rich level under boost to protect the engine. They are also rather useful for mapping engines because they tell you exactly what's going on fuel-wise.
When a sensor dies it generally stops responding to the mixture or responds too slowly. The ECU will detect these conditions and light the EML so you don't need to change the sensors as a matter of course.
Kevin
Hi Kevin,
My EML isn't lit at any time. Does that mean that the initial burn off of oil on starting my 2.6l, due I reckon to failing valve stem seals, will not necessarily be damaging my cats? In other words, does burnt oil contamination cause the same effect as unburnt fuel? I'm hoping to delay taking the heads off for a little longer, but don't want to risk destroying the cats.
Cheers,
Bill.
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The life of both the cats and the Lambda sensors is reduced with excessive oil consumption. If this only happens at startup it probably all burns off by the time the cats and Lambda sensors start working. Difficult to say how much is too much. I have seen 2 figures quoted. For Lambda sensors 1 quart per 1,000 miles (what is a quart? about a litre IIRC) oh, for a metric world!
For catalytic converters 0.0015 lb/bhphr is quoted. So, thumb in the air time - assuming an average speed of 60MPH at an engine output of 40BHP I make that very roughly 1/2 a litre per 1,000 miles. :-/
EDIT: The cats and the lambda sensors are totally separate too. The cats can fail and the Lambda sensors will be none the wiser (except where post-cat sensors are fitted). Only time you'll know cats have a problem is at MOT or if they self-destruct in a spectacular way. A Lambda sensor failure should light the EML though.
Kevin
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1 quart = 1.1365l. I was just going to post that I've got a bit of time probably, and then checked MOT expiry. 8/3/08.
Going to get my answer sooner than I thought. ::)