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Mot Emission Woes


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#1 SidewalkLEW

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Posted 24 July 2020 - 01:42 PM

There are so many posts on here, but my car won't get through it's emissions as part of the mot. I have a 95 mini spi and I have done all the usual things, changed the vacuum pipes, plugged it in and had to change a sensor. Now it passes its CO and HC but I can't get the lambda reading correct. What could be causing the lambda reading to be high, would an exhaust leak do this?



#2 Quinlan minor

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Posted 24 July 2020 - 04:35 PM

Which sensor did you change? this thread might be worth looking at.

http://www.theminifo...ting-out/page-1

 



#3 hunterg30

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Posted 24 July 2020 - 04:56 PM

Make sure you have a genuine Bosch Lambda , copies can cause problems,

#4 koss that was here before

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Posted 24 July 2020 - 05:19 PM

The lambda will read high with the slightest of leaks on the exhaust. If you suspect a leak try a bit exhaust paste an that area. Any good test stations will let you try again without logging it on for retest



#5 SidewalkLEW

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Posted 24 July 2020 - 06:50 PM

Which sensor did you change? this thread might be worth looking at.

http://www.theminifo...ting-out/page-1

It was the coolant temperature sensor in the throttle body, causing it to run rich. But I swapped that out and it brought the CO right down, but now the lambda reading is too high, I guess because it's not running as rich there's way more air to fuel. But I don't know what's causing there to be more air.



#6 SidewalkLEW

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Posted 24 July 2020 - 06:55 PM

Make sure you have a genuine Bosch Lambda , copies can cause problems,

Yeah, I have a genuine one and according to my ecu scanner it is fine. And anyway, I thought that if the lambda sensor was at fault it would cause the car to run rich, and it wouldn't then pass its CO. Its the lambda reading which is too high, which I thought meant there was too much air, in the air to fuel ratio. 



#7 humph

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Posted 24 July 2020 - 09:53 PM

I’ve had similar issues with my lambda sensor twice. The first time the car seemed to be running rich and cutting out randomly. Turned out there was a break in the wire to it just behind the inlet. This is common. Ended up repairing the wire and replacing the sensor which was goosed due to rich running. This first time the fault was intermittent due to Broken wire Connecting/disconnecting.

The second time is in the link in post 2. The coolant temp sensor failed, this quickly leads to the lambda sensor failing also. This second time The issue was intermittent as the sensor failed. It was only after doing numerous running tests with my code reader that I spotted the lambda intermittently not cycling. It should cycle between approx 200 & 500mv rapidly. Rule out electrical supply issues, wires and relays before spending money on sensors.

http://www.theminifo...-oxygen-sensor/

#8 koss that was here before

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Posted 25 July 2020 - 07:47 AM

There are so many posts on here, but my car won't get through it's emissions as part of the mot. I have a 95 mini spi and I have done all the usual things, changed the vacuum pipes, plugged it in and had to change a sensor. Now it passes its CO and HC but I can't get the lambda reading correct. What could be causing the lambda reading to be high, would an exhaust leak do this?

Yes an exhaust leak will raise the lambda, I am a mot tester and have found very small leaks anywhere on the system can cause high lambda.



#9 SidewalkLEW

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Posted 26 July 2020 - 04:24 PM

 

There are so many posts on here, but my car won't get through it's emissions as part of the mot. I have a 95 mini spi and I have done all the usual things, changed the vacuum pipes, plugged it in and had to change a sensor. Now it passes its CO and HC but I can't get the lambda reading correct. What could be causing the lambda reading to be high, would an exhaust leak do this?

Yes an exhaust leak will raise the lambda, I am a mot tester and have found very small leaks anywhere on the system can cause high lambda.

 

Thanks, I had a look and found a couple of exhaust leeks, (successfully repaired them) tried an emission test again, failed again.


Edited by SidewalkLEW, 26 July 2020 - 04:24 PM.


#10 koss

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Posted 30 July 2020 - 03:54 PM

 

 

There are so many posts on here, but my car won't get through it's emissions as part of the mot. I have a 95 mini spi and I have done all the usual things, changed the vacuum pipes, plugged it in and had to change a sensor. Now it passes its CO and HC but I can't get the lambda reading correct. What could be causing the lambda reading to be high, would an exhaust leak do this?

Yes an exhaust leak will raise the lambda, I am a mot tester and have found very small leaks anywhere on the system can cause high lambda.

 

Thanks, I had a look and found a couple of exhaust leeks, (successfully repaired them) tried an emission test again, failed again.

 

What is the lamda reading ? did you get a print out? Did They do the second fast idle test? Maybe a photo of your emissions data could help. If your Co s and Hcs are ok Its got to be an air leak. It helps if everything is nice and hot also.


Edited by koss, 30 July 2020 - 03:56 PM.





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