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Discussion Starter #1
Hello everyoneim not normally on this site but a close friend needs help on his astra 3 the problem it has is high emissions and its the only part of the MOT test it fails on.....we done the following replacementsNew Lambda sensorNew CatalystNew filters all roundNew exhaust all the way throughEven a top end rebuild with new seals and head gasketThe car has NO diagnostic warning lights on and the car goes like stink NO smoke NO nothing its normal to usbut the emissions are high, Can anyone help.......jay. (cavalier CD owner).
 
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JayStone said:
by the way cally nice beemer M3
Cheers :Cool2:

My emissions were the same!
0.003 on fast idle, 1.0% on idle, lucky I know the tester huh? :lmao:
Been told by a very knowledgable source it's the lambda sensors on mine, so would be same for you.
Can't you slip the tester a tenner to rev it up a bit??
 
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If they are over 60K miles old then they will be past their prime, that's for sure.
It is then a good idea to change them, if anything for better mpg.

On idle/low load your car should have AFR 14.7, as you know. A tired O2 sensor will make it look leaner, so the ECU will be throwing more fuel to make it 'look' good.
It's standard practice.
Then the excess carbon piles up on the O2 sensor and it dies even quicker. You don't get an ECU fault until much later, when the sensor is totally dead. It could take years.


What I was told.
 
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Can't think what else it could be - that info comes from a legend :Cool2:

As you know, has to be seriously hot on the cat test. I'm sure yours was as the fast idle was fine.
Can't you get chatty with the tester, show them you've changed everything, and slip them a case of beer?
Sorry I can't be of more help :down:
 

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Discussion Starter #9
thanks Cally

your info has been most helpful just hope that i can get the F***ing car through its test im sure some how.......?

anyway thanks again mate :Cool2:

thumbs up.........
 
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OXYGEN (O2) SENSOR. Used on both carbureted and fuel injected engines since 1981, the oxygen (O2) sensor is the key sensor in the fuel mixture feedback control loop.

Mounted in the exhaust manifold, the O2 sensor monitors the amount of unburned oxygen in the exhaust. On many V6 and V8 engines, there are two such sensors (one for each bank of cylinders).

The O2 sensor generates a voltage signal that is proportional to the amount of unburned oxygen in the exhaust. When the fuel mixture is rich, most of the oxygen is consumed during combustion so there is little unburned oxygen in the exhaust. The difference in oxygen levels between the exhaust inside the manifold and the air outside creates an electrical potential across the sensor’s platinum and zirconium tip. This causes the sensor to generate a voltage signal. The sensor’s output is high (up to 0.9v) when the fuel mixture is rich (low oxygen), and low (down to 0.1v) when the mixture is lean (high oxygen).

The sensor’s output is monitored by the computer and is used to rebalance the fuel mixture for lowest emissions. When the sensor reads "lean" the PCM increases the on-time of the injectors to make the fuel mixture go rich. Conversely, when the sensor reads "rich" the PCM shortens the on-time of the injectors to make the fuel mixture go lean. This causes a rapid back-and-forth switching from rich to lean and back again as the engine is running. These even waves result in an "average" mixture that is almost perfectly balanced for clean combustion. The switching rate is slowest in older feedback carburetors, faster is throttle body injection systems and fastest in multiport sequential fuel injection.

If the O2 sensor’s output is monitored on an oscilloscope, it will produce a zigzagging line that dances back and forth from rich to lean. Take a look at the waveform on the opposite page - that’s what a technician wants to see when he checks the O2 - think of it as a kind of heart monitor for the engine’s air/fuel mixture.

O2 Sensor Strategies: Unheated one- or two-wire O2 sensors on 1976 through early 1990s applications should be replaced every 30,000 to 50,000 miles to assure reliable performance. Heated 3 and 4-wire O2 sensors on mid-1980s through mid-1990s applications should be changed every 60,000 miles. On OBD II equipped vehicles, the recommended replacement interval is 100,000 miles. The O2 sensor’s responsiveness and voltage output can diminish with age and exposure to certain contaminants in the exhaust such as lead, sulfur, silicone (coolant leaks) and phosphorus (oil burning). If the sensor becomes contaminated, it may not respond very quickly to changes in the air/fuel mixture causing a lag in the PCM’s ability to control the air/fuel mixture.

The sensor’s voltage output may decline giving a lower than normal reading. This may cause the PCM to react as if the fuel mixture were leaner than it really is resulting in an overly rich fuel mixture.

How common is this problem? One EPA study found that 70 percent of the vehicles that failed an I/M 240 emissions test needed a new O2 sensor.
 

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Discussion Starter #11
now that was helpful gunna test the lambda tomorrow making sure its working properly.........

thanks cally

P.S love to have a spin in ur M3.....
 
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JayStone said:
now that was helpful gunna test the lambda tomorrow making sure its working properly.........

thanks cally

P.S love to have a spin in ur M3.....
Had one or two spins in it myself, most recent missing someone's front wall my less than an inch........:bust: :lmao:

Good luck with it mate :Cool2:
 

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Discussion Starter #13
thats close enough i think Cally:lmao:

dont wreck the M3......Nooooooooooooooooooooo.

bet you were s***ing yourself when saw the wall coming did'nt you

thanks again Cally been most helpful talk again soon i hope

take it steady.............:Cool2:
 
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Nah, was a sh1t-hot bit of parallel parking. Just was facing the wrong way, on the kerb, and not intending to park at that time :Cool2:
 

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Discussion Starter #15
looool :lmao:

does anybody now the readings what the lambda sensor is so i can test to see if working got the multi-meter ready, if anyone nows i loved to hear from you.

all i can say then Cally is NICE BIT OF PARKING !!!!!!!!!!!

Can you do it all the time though ???????

jay.....:Cool2:
 
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